Top secret files on the Trident missile system and satellite tracking of ballistic missile submarines are believed to have been obtained by the Chinese from the Los Alamos laboratories.

Trident may have been compromised

Since the withdrawal of the RAF's free-fall nuclear bomb, the WE177, Trident is the only nuclear system still deployed in the UK.

The leak of such sensitive information could have a devastating effect on the ability of the UK to maintain and effective nuclear deterrent, experts warn.

Nick Cook, a spokesman for Jane's military information group said getting information on how Trident missiles worked could be the first step in learning how to counter them.

He said Trident used a system whereby multiple warheads were released by each missile to hit individual targets.

He said: "Some are decoys, and if you know which are decoys you could, theoretically, counter them.

"The use of decoys is integral to the Trident system."

Mr Cook said that the leak of information on advances in submarine detection systems was of even more concern.

He said: "A radar system which has been in development by the UK and the US for the last 20 years detects submarines by finding the minute wake that even deep diving subs leave on the surface.

Trident missiles have multiple warheads

"It is incredibly complicated technology, not just the radar system but the computer technology which sifts out different kinds of wave patterns to detect a submarine's wake.

"The Royal Navy prides itself on its ability to conceal its submarines from detection.

"Staying invisible is everything when it comes to nuclear deterrent.

"If you can find a submarine, you can destroy it, either by conventional means or, or if things had escalated to the point where it might be using its nuclear missiles, you could drop a nuclear bomb on it."

He said the incident might reawaken the controversy over the withdrawal of nuclear capability from the RAF.

'Extremely worrying'

Mr Cook said: "When the RAF gave up its nuclear deterrent to the Navy, there was a certain amount of bitterness.

"It may be that some people in Whitehall may now be saying to ministers 'we told you so'.

"They would say that if you rely on one pillar of nuclear deterrent, and if that is damaged in any way, you are wholly exposed.

"The nuclear deterrent is so sensitive that even the suggestion that information has got into the wrong hands is extremely worrying."

'No threat' to subs

Dr Eric Grove, deputy director of the Centre for Security Studies at the University of Hull, said that although the theft of secrets would be an embarrassment, he felt it was not a disaster for the UK's nuclear strategy.

Dr Grove said: "Even if the Chinese knew how to find a submarine, the coverage they would need to detect one with any accuracy, particularly one that was trying to hide itself, would be enormous.

"To do this effectively would probably take up the entire Chinese defence programme.

"The problems of implementing it are very considerable indeed and it certainly doesn't make ballistic missile submarines obsolete.

"I don't want to be complacent, but it isn't a security disaster.

"Even once you have found a submarine, you need the assets to take it on and sink it.

"This would mean having your own fleet of nuclear attack submarines, which the Chinese have made a start on, but don't have anything yet that would pose a threat to British or American submarines."

Dr Grove said the threat to submarines from Chinese missiles was "virtually non-existent" outside of Chinese waters, and one of the advantages of the Trident submarines was that the missiles had a range as far as 5000 miles.