The Sunday Times and the BBC cited senior government and intelligence officials as saying that MI6 agents, the British intelligence agency which supplies the British Government with foreign intelligence, had been pulled out of live operations in hostile countries, without naming them.
The report said the move came after Russia and China were able to decrypt more than one million files held by Snowden, the former American security contractor, after mounting one of the largest leaks in US history.
Senior government sources confirmed that China had also cracked the encrypted documents, which contain details of secret intelligence techniques and information that could allow British and American spies to be identified.
Snowden, a former contractor at the CIA and NSA, downloaded 1.7 million secret documents from western intelligence agencies in 2013 and released details of sensitive surveillance programmes to the media. Two weeks after his initial leak in June 2013, Snowden fled Hong Kong for Moscow where he claimed political asylum.
Snowden, who is wanted in the US, has remained in Russia since fleeing Hong Kong, a special administrative region of China. British Prime Minister David Cameron’s aides confirmed last night the material was now in the hands of spy chiefs in Moscow and Beijing.
A senior Downing Street source said: “It is the case that Russians and Chinese have information. It has meant agents have had to be moved and that knowledge of how we operate has stopped us getting vital information. There is no evidence of anyone being harmed.”