Campaigning yesterday drew to a close in the Government's biggest electoral test since Labour won its third term in power in 2005.

Millions of voters are set to go to the polls today across England, Scotland and Wales, and all the signs are that they are determined to give Tony Blair a bloody nose in his final elections before he quits as Prime Minister.

But the ballots for the Scottish Parliament, Welsh Assembly and local councils in England and Scotland will also be a tough test for Conservative leader David Cameron, who must show that his party's much-vaunted revival stretches outside the south east into areas that have been virtual Tory-free zones since 1997.

Liberal Democrat leader Sir Menzies Campbell needs some sign of progress to reassure internal party critics that he is the man to take them into the General Election of 2009/10.

Strategists argue that he cannot expect big gains, as many of the seats up for grabs were last contested at a highpoint for Lib Dems in 2003.

While Mr Blair, who is expected to announce his resignation as Labour leader next week, has little personally to lose from the results of Thursday's battle, his all-but-certain successor Gordon Brown must be hoping that he does not take over a party reeling from a drubbing of historical proportions.

The fiercest fight is in Scotland, where the latest polls suggest the battle between Labour and the Scottish National Party to form the largest grouping in the Holyrood Parliament is on a knife edge.

Two separate surveys yesterday suggested that Labour was clawing back the SNP's early advantage and there may be only a seat or two between the parties when the results are announced.

A result in line with the polls, giving each party between 42 and 45 seats, would lead to a protracted period of horse-trading as each tries to form a coalition administration in association with Liberal Democrats, Greens, Socialists or (less probably) Tories. Labour could even see itself out of power at Holyrood for the first time since devolution in 1999.

Lib Dems believe they are giving SNP leader Alex Salmond a tough challenge in the Gordon constituency and hope they can reduce him to claiming a seat in the Scottish Parliament through the list system.

In Wales, Labour is fighting to regain control of the national Assembly in Cardiff, which it lost in 2005 when AM Peter Law became an independent.

There is little doubt Labour will remain the largest single party at Cardiff, but with Plaid Cymru leader Ieuan Wyn Jones claiming its vote is in "meltdown" it may lose enough seats to allow a combination of nationalists, Liberal Democrats, Tories and independents to form a coalition and remove it from power.

In England, Mr Blair's party is simply hoping to keep down the number of seats it loses on councils up and down the country.

Predictions are that Labour could haemorrhage as many as 750 of the 2,385 seats it is defending, and the party's control of authorities such as Sheffield, Blackpool, Lincoln, Plymouth and Blackburn with Darwen is under threat.

After a string of poor performances in local elections, Labour holds just 28 per cent of Britain's 21,892 council seats - its weakest position since 1973.

Conservatives hope to add to their tally by 600 to 700, and seize control of authorities such as Bournemouth, Bury and Brighton and Hove.

But a more important indication of whether the party is successfully preparing the ground for a serious assault on power in 2009/10 will be the Conservatives' share of the vote.

Previous Tory General Election victories in 1979 and 1992 were preceded by local authority ballots in which they secured around 45 per cent of the vote, and the Tories will be looking for a similar result today.