The Sinn Fein president was shot five times as he travelled with three colleagues through Belfast city centre to the Magistrates Court.

However, a UDR patrol rammed the murder vehicle soon after and three men were arrested - John Gregg, Gerard Welsh and Colin Gray.

Several years ago a book, Big Boy's Rules, by journalist Mark Urban alleged that a British military intelligence source had confirmed that a UDA agent had tipped police off in advance.

And today it was reported that an unnamed retired RUC detective had supported the claim that a Special Branch informer told his handlers a week before the attack that it was to take place.

Mr Adams said he has instructed his solicitor to write to Police Ombudsman Nuala O'Loan, following the report in the Andersonstown News newspaper.

"This is not the first time that a source from within the British system has confirmed that the UDA gang who carried out the attack were colluding with the Special Branch and British Military Intelligence," he said.

"I have asked my solicitor to write to Nuala O'Loan and ask that his latest information be thoroughly investigated."

The move came the day after Mr Adams, who police have told is currently facing a death threat from dissident republicans, held his first direct meeting with Chief Constable Sir Hugh Orde.