Around 300 current and former members of the police, Army and MI5 held a dinner to acknowledge the changeover.

A police spokesman said the completion of the transfer of powers was " on-track", but would make no further comment.

In an interview last year, Assistant Chief Constable Peter Sheridan predicted that the changeover would take place towards "the back end of 2007".

Senior security sources say there remain some minor "protocol" issues to be resolved between the police, MI5 and the NIO, but that most procedural arrangements had been put in place.

During interviews last year, ACC Sheridan, who is responsible for crime operations, said he had set out five principles which were non-negotiable covering MI5's working practices and accountability.

But the SDLP's Alex Attwood (right) remains unconvinced that the necessary accountability measures are in place.

He has pointed out that there are no 'real-time' mechanisms in place to examine ongoing MI5 operations and argues that the review mechanism which covers MI5's activities has not once upheld a complaint against the National Intelligence Service in Britain.

Chief Constable Sir Hugh Orde and other senior officers were among guests who attended the dinner, at the Stormont Hotel.

Guest speaker - former Special Branch chief Chris Albiston - said that pride should be taken in the fact that the current successful operational methods employed in Britain between the police and MI5 were pioneered in Northern Ireland and were recognised as a "beacon of good practice".

Mr Albiston said that few were prepared to acknowledge the successes achieved locally by those methods and the co-operation pioneered in Northern Ireland.

He said that many people were prepared to denigrate the intelligence efforts which helped bring the terrorists to the negotiating table.

He added: "And, I regret to say, it seems to be meekly accepted by some of those who have a duty to rebut it in the most robust manner. In an attempt to belittle your efforts and to rewrite history, the word 'collusion' has been bandied about in a disgraceful, irresponsible and potentially libellous fashion."

Referring to the inquiries being conducted into past events, the former ACC said: "Everyone is aware of the vulnerability of the Executive - some of whose members would really not be too keen on any public revelations of the truth about the last 35 years.

"But, as the (Police) Ombudsman continues to impersonate the blind man searching at midnight in the dark, unlit, windowless room for the black cat, perhaps it's about time that she publicly accepted what she has so frequently been told - that the black cat she's looking for simply isn't there."