TONY BLAIR is expected to be quizzed within weeks by police probing the "cash for honours" scandal after the revelation that Alan Milburn has been interviewed.

The Darlington MP and former Cabinet minister said yesterday he had become the latest senior Labour figure to be questioned - as a witness - by Scotland Yard detectives.

It then emerged that police had asked up to five Cabinet ministers for interviews, with Health Secretary Patricia Hewitt known to be among them.

Furthermore, all Cabinet members at last year's General Election - apart from Mr Blair - are thought to have received letters from, or been contacted by, detectives.

Last night, Angus MacNeil, the Scottish Nationalist MP who initiated the inquiry, said: "I have no doubt where this is going - and that's directly up the road to Downing Street. It is now only a matter of time before the Prime Minister is questioned over this issue. It is becoming ever clearer that Mr Blair is not in charge of events over this - events are controlling him."

Mr Milburn said: "Following a request from the police, I have been interviewed as a witness. The police stressed I was not a suspect and the interview did not take place under caution."

It emerged earlier this year that Labour borrowed £14m to fight the election. Four of those who lent money were later nominated for peerages.

A corruption investigation was launched into possible breaches of the 1925 Honours Act and the 2000 Political Parties Act.

The inquiry started closing in on Mr Blair in July, when Lord Levy - Labour's chief fundraiser - was arrested and interviewed.

The letters sent to Chancellor Gordon Brown and most of Labour's senior figures make clear they will not be quizzed in person by detectives.

The fact that the Prime Minister is being treated differently immediately fuelled speculation at Westminster that he will be questioned under criminal caution.