A tranche of data released by former CIA employee Edward Snowden has been described as the ‘most catastrophic loss to British intelligence’ by former No.10 adviser, Sir David Omand.
Speaking to the Times Omand said he assumed the data was now being analysed by Russia and China and was worse than that divulged by the Cambridge spy ring in the 1950s.
Omand said: “You have to distinguish between the original whistleblowing intent to get a debate going, which is a responsible thing to do, and the stealing of 58,000 top-secret British security documents and who knows how many American documents, which is seriously, seriously damaging.
“The assumption the experts are working on is that all that information or almost all of it will now be in the hands of Moscow and Beijing.
"It's the most catastrophic loss to British intelligence ever, much worse than Burgess and Maclean in the 1950s."
The Guardian says it will continue to publish further leaked documents and said it was right to do so.
In September, Chris Boffey, former news editor of the Observer, Sunday Telegraph and the Mirror and onetime special adviser to the Labour government, described Snowden as a spy - even if it wasn't his intention - after he divulged the information he had to the Guardian.