How has Mr Mandelson's Sunday Times article revived the passport affair?

Mr Mandelson is now disputing the main reason behind his resignation - that he called the Home Office on behalf of the Hinduja brothers and then covered it up.

He says he has checked back with aides, who are sure they dealt with the Home Office, not him.

He says he was rushed into a resignation and regrets not fighting to prove the facts.

Is he right about the call?

The disputed existence of any telephone call between Mr Mandelson and Home Office Minister Mike O'Brien will now be down to the independent inquiry to establish. Tapes may exist, and there are likely to be notes on both sides.

Mr Mandelson says he was led to believe the call had taken place on the basis of Mr O'Brien's recollection, not his own, and hence changed his story.

He is putting his faith in the inquiry verdict. But Home Secretary Jack Straw is insisting that the call did take place - and is understood to have reminded Mr Mandelson of it very shortly before the now ex-Northern Ireland secretary denied to a newspaper that any such contact with Mr O'Brien took place.

How will Mr Mandelson prove himself?

This is what must be worrying Downing Street. In the Sunday Times, he pledges to clear his name, and he refers to his article as a "starting point".

If someone with as much inside information as Mr Mandelson continues to cause headaches for the government, it could be damaging to the party in the run-up to the general election.

What can Downing Street do?

Cabinet ministers lined up on Sunday to discredit Mr Mandelson's "fightback".

More damaging for Downing Street, however, are allegations that the prime minister's official spokesman, Alastair Campbell, set out in his regular briefing of Sunday newspaper political editors to discredit Mr Mandelson.

Mr Campbell denies any rift and says he was misinterpreted when he said Mr Mandelson was "slightly detached".

But it certainly appears that a war of briefing between the two formerly close spin doctors is being waged.

What are the Tories making of this?

They have stepped up their attack on Downing Street's handling of the resignation - they want answers as to why Mr Mandelson was forced to go.

But they also want the inquiry into the Hinduja affair widened, to examine whether the billionaire Indian brothers were given preferential treatment in a passport application, and to make clear what other links the brothers have to the Labour Party.

Europe Minister Keith Vaz is foremost among those with close ties to the brothers who is accused ot having lobbied on their behalf.