TONY BLAIR was on course to secure a record third successive General Election victory last night - but with a much reduced majority and a question mark over his continued leadership.

Labour's fear that its support in marginal seats would not hold up appeared to be borne out in a joint BBC/ITV poll that suggested the Government's majority would be cut from 160 to 66.

Although opinion polls have consistently predicted a Labour win, such a drastic cut in the Government's majority would be seen as a blow to the Prime Minister.

If true, it would heap further pressure on Mr Blair - who is 52 today - to step down sooner rather than later into his third term.

The Prime Minister plans to serve a full term, before a smooth hand-over of power when he steps down, but maverick backbenchers will inevitably call for him to go earlier and allow a new leader to settle in to the role.

Left-wing MPs, who have not forgiven the Prime Minister for taking Britain to war in Iraq, are expected to start plotting to unseat him if the Labour majority is slashed.

Chris Mullin, Labour candidate for Sunderland South, became the first MP to be returned to Parliament shortly before 10.45pm.

After seeing his vote slip by 5.3 per cent from 19,921 in 2001 to 17,982, he warned: "We now have a chance to shape the lives of an entire generation. We must use it wisely."

Bill Etherington held on to Sunderland North with a handsome 15,719 majority but, once again, the Labour vote was down - by 8.3 per cent - with a 5.1 per cent swing to the Conservatives.

Fraser Kemp held on to Houghton and Washington East, but his 22,310 vote was down 8.9 per cent.

Former Labour minister Claire Short, who resigned over the Iraq war, said: "A smaller majority might be good for our Government.

"If there was a little bit more discussion, and respect for Parliament and all the different opinions in the Labour Party, it might improve the quality of the Government."

Tory former Cabinet minister Michael Portillo said: "On these results, I would have thought not Gordon Brown himself but the Brown supporters will be wondering how quickly they can move Tony Blair out of Downing Street.

"It would be possible, I think, to portray this result as disappointing and that the key factor in the campaign was that this time Tony Blair was not an electoral asset.

"He was becoming a liability."

The BBC/ITV poll gave Labour a total of 356 seats - down from 409 in the last Parliament, taking its majority from 161 to 66.

The 209 seat prediction for the Tories would be a gain of 45.

Charles Kennedy's Liberal Democrats would see their number of seats dip slightly from 55 to 53, according to the poll of more than 15,000 voters in 120 polling stations across the UK.

Deputy Prime Minister John Prescott said the final result was "just too difficult to call".

Darlington MP Alan Milburn, who co-ordinated Labour's campaign, said the exit poll was interesting, but urged caution.

"These polls have been wrong before. I guess they will be wrong again," he said.

"But it does seem to indicate that there will be a Labour government and that's welcome news.

"Tony Blair would be only the second Prime Minister in history to win three General Elections in a row, with a mandate and a majority for a New Labour programme of government."

Mr Milburn denied that a slashed majority indicated that, without Gordon Brown, the party's campaign would have been in serious trouble.

"No, I don't think that. I think we really do just have to wait and see. It's very early days.

"As far as our campaign is concerned, we ran precisely the campaign we said we would - rooted in our strengths, our leadership, our values, our record on the economy, investment and improvement in the public services.

"I think what we managed to do was expose the Conservative Party as a party that is pretty unchanged, unreformed.

"It ran a pretty nasty right-wing campaign. It used to be a One Nation party, it turned into a one-issue party. That issue was immigration."

Polls closed after an intensive three-and-a-half week campaign, with Mr Blair, Tory leader Michael Howard and the Lib Dems' Charles Kennedy criss-crossing the country clocking up thousands of campaign miles.