UK intelligence agents have been moved because Russia and China have access to classified information which reveals how they operate, a senior government source has confirmed.
The story was originally broken by the 'Sunday Times', which revealed how Moscow and Beijing have deciphered documents stolen by whistleblower Edward Snowden.
Reacting to the reports yesterday, UK government sources confirmed that the countries "have information" that led to agents being moved but added there was "no evidence" that any had been harmed.
Mr Snowden leaked the original data two years ago.
The former CIA contractor, now living in Russia, left the US in 2013 after leaking details of extensive internet and phone surveillance by American intelligence to the media.
His information made international headlines in June 2013 when the 'Guardian' newspaper reported that the US National Security Agency was collecting the telephone records of tens of millions of Americans.
Mr Snowden is believed to have downloaded 1.7 million secret documents before he left the US. The government source said the information obtained by Russia and China meant that "knowledge of how we operate" had stopped the UK getting "vital information".
BBC political correspondent Chris Mason said the problem for UK authorities was not only the direct consequence that agents had been moved, but also the opportunity cost of those agents no longer being in locations where they were doing useful work.
A former cabinet minister has joined campaigners in questioning the timing of the "convenient" claims that spies had been moved.
The agents were reportedly removed from live operations after Moscow and Beijing cracked the encryption on the archive of documents taken by Mr Snowden. 'The Sunday Times' had cited sources in Downing Street and the security services saying that, as well as it being necessary to remove field agents, "vital information" has been put out of reach of Britain's spying agencies because of details in the stolen files about their operating methods.
But while one Home Office official was quoted as saying that Mr Snowden had "blood on his hands", a Downing Street source claimed that there was "no evidence of anyone being harmed". There was no indication of when in the last two years the agents were withdrawn. The leaks from Government sources were greeted with concerns that they are part of a propaganda drive to shore up public support for mass data collection by the security agencies.
The human rights group Liberty pointed out that the claims come days after a report by Britain's counter-terrorism watchdog said new, clearer laws are required to frame the eavesdropping powers of the security services and the current situation is "undemocratic, unnecessary and - in the long run - intolerable".
David Anderson QC said the intelligence agencies should be allowed to retain controversial powers to collect bulk communications data but said ministers should be stripped of their role in granting surveillance warrants.
Shami Chakrabarti, director of Liberty, said: "Last week, David Anderson's thoughtful report called for urgent reform of snooping laws - that would not have been possible without Snowden's revelations.
"Days later, an 'unnamed Home Office source' is accusing [Snowden] of having blood on his hands. The timing of this exclusive story from 'securocrats' seems extremely convenient."
Andrew Mitchell, the former International Development Secretary, agreed it was "no accident" that the claims concerning the impact of Mr Snowden's actions had emerged in the wake of Mr Anderson's report and the revival of the Government's snooper's charter legislation on communications interception.
Mr Mitchell told BBC Radio 5 Live: "There is a big debate going on. Anderson is going to be a very important part of that. We're then going to have legislation brought back to Parliament about the way in which individual liberty and privacy is invaded in the interests of collective national security." (© Independent News Service)