Ministers were urged yesterday to take a more robust stance with Beijing over claims that Chinese hackers have broken into computer systems in Whitehall.
The call came from a Labour member of the influential House of Commons Foreign Affairs Select Committee, Andrew MacKinlay, who said it seemed clear the cyber-attacks had the acquiescence, at least, of the Chinese authorities.
A national newspaper report quoted unnamed Whitehall officials as saying that the hackers - some believed to come from the People's Liberation Army - have hit the network of the Foreign Office and other key departments.
And they said an incident which shut down part of the House of Commons computer system last year was discovered to be the work of an organised Chinese hacking group.
The Foreign Office yesterday refused to discuss the claims, saying only: "We do not comment on security issues."
But Mr MacKinlay insisted that the public and Parliament had a right to be told if the UK was becoming the target of a phenomenon known as "patriotic hacking", in which computer experts use their skills to attack the vital networks of perceived enemies of their nation.
He said his attempts to prise information from the Government about the scale of the problem had been stonewalled by ministers including former Foreign Secretary Jack Straw, now Justice Secretary.
"I am frustrated," Mr MacKinlay said. "This is clearly an area where the Government have decided not to comment. My questions were clearly unwelcome. The security and intelligence services and Foreign Office did not want this to come out into the public domain.
"This is happening against a backdrop where, on a whole range of foreign policy issues, the British Government is very weak. They seek to appease the Chinese. They should be more robust and indignant.
"We do not send out the right signal on this. Beijing know about it and, at the least, they acquiesce in it."
There was clearly a political motive behind the attacks, said Mr MacKinlay, who dismissed the idea the hackers were simply "computer nerds" acting alone.
The most plausible theories on why the Chinese authorities might choose to foster patriotic hacking were either to test its potential as a weapon for use in future conflicts or simply to send a signal to other great powers that they have the capability to do so, he said.
Alex Neill, head of the Asia Security Programme at the Royal United Services Institute, told The Guardian cyber-attacks by the Chinese had been taking place for at least four years. He said they reflected a new PLA doctrine of "pressure point warfare" - attacking specific nodes to leave an adversary paralysed.
In response to a parliamentary question tabled by Mr Mackinlay last year, the then Home Secretary Charles Clarke revealed the National Infrastructure Co-ordination Centre had issued a warning in 2005 of "concerted Trojan e-mail attacks from the Far East against UK Government and business interests".
The scale of attacks was described as "almost industrial", said Mr Clarke.
But when Mr MacKinlay tackled Mr Straw on the issue during an appearance before the Foreign Affairs Committee in Westminster, he got little information.
"I cannot help feeling that the Chinese government authorities are either the inspirers of this or with full knowledge and with full consent allowed this to happen from China and that for wider foreign policy reasons your department do not want this raised," the Thurrock MP told the then Foreign Secretary in March 2006.
"This is a very serious matter. It is an act of terrorism and it is emanating from China."
Mr Straw replied: "You will have to excuse me, but I am not intending to add to anything I have already said on this issue, which I know is not a great deal."