Blair's moment of truth (Top-up fees)

Tony Blair is on the brink of a dramatic Commons defeat in the same nightmarish week that the year-old question of why he went to war in Iraq returns to haunt him.

An Independent on Sunday poll of Labour MPs indicates that at least 81 still plan to defy the Government in Tuesday's critical vote on the Higher Education Bill, administering the first of a series of high-voltage political shocks to Mr Blair's premiership. He hopes to restore his authority at the end of the week with a vote of confidence from the Commons - if needed - followed closely by a Cabinet reshuffle.

"In this job you spend the entire time at risk, so there is not a moment when you are not," he said.

Charles Clarke, the Secretary of State for Education, who is battling to save Mr Blair's plans for universities, is tipped to take over at the Ministry of Defence after the publication of Lord Hutton's report into the death of Dr David Kelly, which is expected to criticise the MoD.

The current Secretary of State, Geoff Hoon, is expected to go - but whether he is moved to another department or sacked will depend on what Lord Hutton says.

Mr Blair himself will escape criticism in Lord Hutton's report, but Mr Hoon is among several people from the Government and the BBC who have been warned in writing of what is to be said about them. Alastair Campbell, his former director of communications, the BBC journalist Andrew Gilligan and its Director General, Greg Dyke have also been warned they face criticism.

Mr Clarke's transfer is being planned in Downing Street in the hope of drawing a line under the bitter controversy over the proposal to make students pay up to £3,000 a year in tuition fees, depending on which university course they choose. Speaking to The Independent on Sunday, Mr Clarke admitted that the Government could be defeated on Tuesday, unless rebel Labour MPs could be persuaded to change their minds. A defeat would probably be followed by a confidence vote - the first since Labour came to power more than six years ago.

The prospect of defeat is borne out by this newspaper's survey of 143 Labour MPs, showing very little shift of opinion in the Government's favour. Using the survey, a list has been compiled of 81 Labour MPs who are still saying they intend to vote against the Government - enough to deny Labour its overall Commons majority. The rebels themselves say they have a list of 101 names, plus 20 who are expected to abstain.

The Cabinet was warned last week of the risk of defeat by the Chief Whip, Hilary Armstrong. She indicated they were short of 35 votes, which tallies with The Independent on Sunday figures suggesting that the Government could lose by around 319 to 286.

But Mr Clarke claimed: "The problem about all the surveys, including yours, is that there is a significant number of people who are deciding what to do over the weekend. All of these people have been marked down as against the Government, which is why Hilaryis saying - quite rightly - that we haven't got the votes.

"If the Bill does not go through, we have no Plan B. We have no alternative set of proposals around the corner. This really is the time of choice. They have got to decide where they are. I am confident that we will win the vote."

The Chancellor, Gordon Brown - who has also had doubts in the past about top-up fees - said in an interview to be broadcast today by GMTV: "The proposals are radical, they are reforming, and I believe Tony Blair deserves support for putting them forward. We are facing a problem that previous governments have not."

Rebel leaders came under angry attack from a former cabinet minister, Jack Cunningham, who told BBC Radio 4's Today programme: "I don't see why a few disgruntled ministers should now be planning and organising the defeat of the Government and the Prime Minister, not for any good reasons of policy or principle but simply because of a few bruised egos."