Tony Blair is heading for a record third term with a three-figure majority, but potentially the lowest share of the vote for any governing party in modern times, a Populus poll for The Times and three others suggest tonight.

But tomorrow's result promises to be the most unpredictable since 1992, after signs that the Liberal Democrats could be gaining ground in several Conservative seats.

Overall the polls did not make good reading for the Conservatives. The Populus survey suggests that in the final days of the campaign Labour has been holding on to its support and, along with the Liberal Democrats, taking the majority of votes of those who have recently made up their mind.

All the polls suggest a slight strengthening of support for the Liberal Democrats, possibly explaining why Mr Blair and his party have concentrated their fire on them in last few days.

The prospect of all parties losing seats as a result of the ferocious battle in the marginals appeared real and all three main party leaders fanned out to marginal seats tonight at the end of the last day of campaigning.

The Populus poll, undertaken on Monday and Tuesday, shows that late deciders and the still undecided are inclining towards Labour, and especially the Liberal Democrats, and against the Tories.

Labour is shown on 37.9 per cent. This would be a drop of 4.1 points since the 2001 election, a lower share than any victorious Prime Minister has ever had. Moreover, Populus estimates that turnout may be only 57 per cent, down from 59 per cent in 2001. This means that Labour would have the backing of less than a quarter of the electorate.

But the Tories could be heading for an even worse result than in 2001 with a projected share of the vote of 31.7 per cent, down one point, barely above their record low share in 1997.

The main beneficiaries have been the Liberal Democrats, 2.6 points up since 2001 at 21.4 per cent, and other parties, up 2.6 points at 9 per cent.

The three other polls tonight, from NOP, ICM and You Gov, reported similar figures, which if confirmed at the ballot box today would indicate a Labour overall majority of more than 100, and possibly up to 130. However, regional and local variations could help the Tories around London. But any Lib Dem gains from the Tories would not affect the size of the Labour majority.

This morning the Prime Minister held his final press conference of the month-long campaign in Lady Thatcher's old constituency of Finchley, now a Labour marginal, telling voters that they faced a stark choice between a Labour or a Conservative government.

Michael Howard, the Conservative leader, took heart from the victory in last night's Champions League semifinal of his favourite team, Liverpool, who beat Chelsea 1-0 at Anfield.

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