Detectives investigating the cash-for-honours affair have uncovered a "hidden" computer network in Number 10 from which crucial emails appeared to have been deleted, according to claims.

Downing Street issued a swift denial to the allegations made by ITV News, which claimed the existence of a second IT system in the building was revealed to police by a witness over recent weeks.

The information reportedly led to the arrest of one of Tony Blair's closest aides, director of Government relations Ruth Turner, last week.

ITV also alleged that officers discovered emails last autumn which were apparently exchanged between Labour fundraiser Lord Levy, Ms Turner and Mr Blair's chief of staff Jonathan Powell.

They were said to be "indiscreet" and referred directly to "K's and P's" being offered to those who have donated money. The suggestion was that K could stand for knighthood and P for peerage.

A Downing Street spokesman said: "This story is untrue. There is no second computer system in No 10. There are no emails of the type that seem to be described. The police have had full access to the system and full co-operation. "The police have not put any of this to us."

Some emails on the second computer network appeared to have been deleted after the police inquiry was launched, ITV said.

Detectives reportedly now expect the inquiry to run until the spring, but charges remain unlikely because of the difficulties proving "criminal intent".

The arrest of Ms Turner - one of the Prime Minister's closest aides - sent shockwaves through Westminster last Friday. The police decision to detain Ms Turner at her London home in a dawn raid led to accusations from Government ministers and Labour peers that they were being heavy-handed and "theatrical".

There were also indications that the move may have been due to new information suddenly coming to light rather than designed to "shake up" suspects.

Well, this is just fantastic. Following the claims that there's no real problems with e-voting machines, almost immediately followed by reports of massive fraud with e-voting machines in Brazil, Alex Halderman is pointing out that Diebold, in their infinite wisdom, are making it ridiculously easy to break into their machines. Halderman was a part of the team that showed that Diebold's locks on their e-voting machines used a default key that was common to many hotel minibars and could be found easily in many places. However, the researchers who noted this were still careful never to show the actual key, preferring not to help anyone who seriously intended on breaking into the machines. Diebold, on the other hand, isn't so careful. The company, that has continually played down reports of security flaws is apparently selling the very key you need to break into their boxes on their online site... with a picture of the key. You need to be a Diebold account holder to buy it, but anyone can look at the key and then figure out how to make their own copy -- and, in fact, that's exactly what someone did. He used the picture to cut his own keys and sent the keys to Halderman, who found that two of the three keys opened the Diebold locks with ease. The guy who discovered this notified Diebold a month ago, but Diebold did not respond and has not removed the image of the key from their website.

Electronic voting machines count about 87% of the votes cast in America today. But are they reliable? Are they safe from tampering? From a current congressional hearing to persistent media reports that suggest misuse of data and even outright fraud, concerns over the integrity of electronic voting are growing by the day. And if the voting process is not secure, neither is America's democracy. The timely, cautionary documentary HACKING DEMOCRACY exposes gaping holes in the security of America's electronic voting system.

In the 2000 presidential election, an electronic voting machine recorded minus 16,022 votes for Al Gore in Volusia County, Fla. While fraud was never proven, the faulty tally alerted computer scientists, politicians and everyday citizens to the very real possibility of computer hacking during elections.

In 2002, Seattle grandmother and writer Bev Harris asked officials in her county why they had acquired electronic touch screen systems for their elections. Unsatisfied with their explanation, she set out to learn about electronic voting machines on her own. In the course of her research, which unearthed hundreds of reported incidents of mishandled voting information, Harris stumbled across an "online library" of the Diebold Corporation, discovering a treasure trove of information about the inner-workings of the company's voting system.

Harris brought this proprietary "secret" information to computer security expert Dr. Avi Rubin of Johns Hopkins University, who determined that the software lacked the necessary security features to prevent tampering. Her subsequent investigation took her from the trash cans of Texas to the secretary of state of California and finally to Florida, where a "mini-election" to test the vulnerability of the memory cards used in electronic voting produced alarming results.

As the scope of her mission grew, Harris drew on the expertise of other computer- science experts, politicians and activists, among them: Andy Stephenson, candidate for secretary of state in Washington state; Susan Bernecker, Republican candidate in New Orleans; Kathleen Wynne, an activist from Cleveland; Dr. Herbert Thompson, chief security strategist, Security Innovation, Inc.; Ion Sancho, supervisor of elections for Leon County, Fla.; and Harri Hursti, a computer-security analyst. Academics, public officials and others seen in interview footage include: Deanie Lowe, supervisor of elections, Volusia County, Fla.; Mark Radke, marketing director of Diebold; David Cobb, presidential candidate, Green Party; and Rep. Stephanie Tubbs-Jones of Ohio.

Diebold software, or other software like it, is installed in thousands of counties across 32 states. David Dill, professor of computer science at Stanford, says the problem is that there are "lots of people involved in writing the software, and lots of people who could have touched the software before it went into that machine. If one of those people put something malicious in the software and it's distributed to all the machines, then that one person could be responsible for changing tens of thousands of votes, maybe even hundreds of thousands, across the country."

In Florida, Leon County supervisor of elections Ion Sancho presided over a trial "mini-election" to see if the vote could be hacked without being detected. Before votes were actually cast, computer analyst Harri Hursti "stuffed the ballot box" by entering votes on the computer's memory card. Then, after votes were cast, the results displayed when the same memory card was entered in the central tabulating program indicated that fraud was indeed possible. In other words, by accessing a memory card before an election, someone could change the results - a claim Diebold had denied was possible.

Ultimately, Bev Harris' research proved that the top-secret computerized systems counting the votes in America's public elections are not only fallible, but also vulnerable to undetectable hacking, from local school board contests to the presidential race. With the electronic voting machines of three companies - Diebold, ES&S and Sequoia - collectively responsible for around 80 percent of America's votes today, the stakes for democracy are high.

See http://www.hbo.com/docs/programs/hackingdemocracy/index.html

A Russian general has criticised a US plan to place an anti-missile system in Poland and the Czech Republic, calling it a threat to Moscow, but a senior US official denied that was its purpose.

"Our analysis shows that the placing of a radio locating station in the Czech Republic and anti-missile equipment in Poland is a real threat to us," said space forces commander Lieutenat-General Vladimir Popovkin, according to Russian news agencies.

US assistant secretary of state Daniel Fried told the Polish daily Rzeczpospolita that Moscow had nothing to fear. "We believe that building infrastructure of the anti-missile shield in Poland and the Czech Republic will significantly boost the defences of a united Europe," Fried said. "I want to stress that the anti-missile system is not aimed at Russia."

The US is investing around $10 billion per year in its Missile Defence Initiative (MDI) system, which would combine long-range radar and interceptor missiles to detect and shoot down ballistic missiles carrying nuclear, bacteriological or chemical warheads.

Officials in Washington DC made an offer to Warsaw and Prague last week to start detailed negotiations on hosting parts of the system. The negotiations could take months, says Fried, and Poland's parliament would have to endorse a decision to host the missiles amid public doubts.

Under the proposal, Poland could be the base for underground rocket silos housing approximately 10 interceptor missiles in total, while the Czech Republic would host a radar system to track incoming ballistic missiles. The interceptors would be designed to strike them as they cruised through space.

US officials say this portion of the shield will protect it and continental Europe from missiles that could be fired from Iran or other "rogue regimes".

This point of view has some support from Baker Spring, a defence analyst at the Heritage Foundation, a conservative think-tank in Washington DC. "My judgment is that the primary purposes of that site would be to counter intermediate to long-range missiles primarily out of the Middle East region," Spring told New Scientist.

Russia should not be too concerned, he says, as the number of missiles they have could easily overwhelm the defences planned for Poland and the Czech Republic. But Popovkin remains sceptical about the stated target. "It's very doubtful that elements of the national US missile defence system in eastern Europe were aimed at Iranian missiles, as has been stated," he said.

Theodore Postol, a professor of science, technology and national security policy at the MIT, US, also doubts that the proposed installations would be effective against a threat from Iran. He says that by the time Iran developed intercontinental ballistic missiles that could conceivably strike the US, they would probably have long-range missiles to knock out the Eastern European facilities first.

Postol thinks that this may be just a plan to involve as many countries as possible to ensure the survival of MDI. "I read it as having little or no technical merit," Postol told New Scientist.

Indeed, Postol doubts the effectiveness of ground-based interceptors in general, as the interceptors' infrared sensors could be fooled by decoy balloons released with a warhead.

AN ANTI-WAR protester who was refused boarding on a Qantas flight to London because he wore a provocative T-shirt has issued a challenge to the airline to fly him home dressed the same way.

Allen Jasson, 55, an IT specialist living in London, is staying with his daughter in Melbourne after he was refused entry to the flight to London at Melbourne Airport on Friday.

Mr Jasson said he risked missing his chance of permanent residency if he spent more than two months out of Britain. He said he was seeking legal advice to challenge the airline's policy and recover costs.

Mr Jasson was told he could not fly last Friday from Melbourne Airport while wearing a T-shirt that said US President George Bush was the world's number one terrorist.

It was not the first time Mr Jasson had been told to remove his T-shirt. On December 2, a security guard at London's Heathrow Airport told him, "You won't be flying with that on".

Domestic carrier Virgin Blue took the same action when Mr Jasson tried to catch a connecting flight to Adelaide, but on a return flight to Melbourne with Qantas on Friday, he wore the shirt.

But when he approached the gate manager at Tullamarine on Friday, he was ordered to take it off.

Mr Jasson said he cleared international security checks and arrived at the departure lounge in Melbourne for the flight home when he approached the gate manager. He told the manager that it was "good Qantas relented on the business of the T-shirt" and said he was owed an apology. The manager, then noticing the T-shirt, said Mr Jasson would have to remove it or he couldn't fly.

Mr Jasson said it was his right to express "a popular political" view and denied it was an attention-seeking exercise. "It's game on, Qantas. They are going to fly me home wearing this T-shirt," he said. "I have made up my mind that I would rather stand up for the principle of free speech."

A Qantas spokesman said: "Whether made verbally or on a T-shirt, comments with the potential to offend other customers or threaten the security of a Qantas group aircraft will not be tolerated."

The arrest of one of Tony Blair's top aides in the cash for honours row was made after fresh information was uncovered during a search of the Number 10 computer system, according to reports.

The investigation put police at loggerheads with politicians after Ruth Turner was arrested in a dawn swoop on her home.

The News Of The World said it was informed by sources within the Crown Prosecution Service that a "mole" within Downing Street told the police about potentially incriminating emails.

An independent IT expert was then sent in by detectives, with the permission of Downing Street, to look through communications records, it claimed. But the Sunday Telegraph suggested that detectives had obtained high-level permission to "hack" into the IT system remotely.

Senior Labour figures were quick to criticise Scotland Yard's tactics after officers arrived at the home of Ruth Turner at 6.30am on Friday. Culture Secretary Tessa Jowell and former cabinet colleague David Blunkett both said they were "bewildered" and others accused the police of "theatrics".

But Glen Smyth, chairman of the Metropolitan Police Federation, which represents rank-and-file officers, has accused them of trying to "influence the inquiry" and putting them under "undue" pressure. And the Labour chair of the Metropolitan Police Authority, Len Duvall, said no-one should try to "manipulate or pressurise" officers.

Ms Turner, Downing Street director of Government relations, was questioned on suspicion of perverting the course of justice before being released without charge. Ms Turner, who was interviewed by police twice last year, refutes "any allegations of wrongdoing of any nature whatsoever" and insisted she had always offered full co-operation.

As Mr Blair's "gatekeeper" - a post previously held by close allies Anji Hunter and Baroness (Sally) Morgan - Ms Turner holds a key position in Number 10, reporting direct to chief of staff Jonathan Powell and playing a role in controlling access to the PM.

Ms Turner, 36, was appointed as a Downing Street special adviser in May 2005, having previously served on Labour's ruling National Executive Committee. She stood for the party in the 1999 elections to the European Parliament.

She is the fourth person - and the first salaried Government official - to be arrested in the inquiry, after Mr Blair's personal fundraiser Lord Levy, major Labour donor Sir Christopher Evans and headteacher Des Smith.