Alan Fisher, Al Jazeera's correspondent in London, said "it's clear that this is going to be about the economy. It's all going to come down to money".

'Clear message'

Brown said he intended to "take to the people a very straightforward and clear message - Britain is on the road to recovery and nothing we do should put that recovery at risk".

Labour argues that Brown has steered Britain through turbulent economic times and to hand over now to an inexperienced opposition would jeopardise recovery.

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The opposition Conservative party, led by David Cameron, has said that they would cut the deficit faster than Labour but have now promised to exempt most workers from a rise in payroll tax that Labour plans from 2011.

That has won approval from the party's traditional business supporters.

"We're fighting this election for the great ignored. Young, old, rich, poor, black, white, gay, straight," Cameron said in a statement, showing how he has tried to make his party more inclusive.

Nick Clegg, leader of the Liberal Democrat party, insisted that the contest would not just be a two-way fight between Labour and the Tories.

"This is a choice now between the old politics of the two old parties and something new, something different, which the Liberal Democrats offer," he said.

Expenses scandal

Fraser Nelson, political editor of the UK's Spectator magazine, said it would be a "genuinely close election" where anything could happen.

"Normally you can tell months before who's going to win," he told Al Jazeera. 

"The Conservatives are nowhere near ahead as they should be when you think about the economic circumstances. And it's not impossible that Gordon Brown may even squeeze past.

"So anything's up for grabs and it makes it a very exciting election to follow."

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The election to be held on May 6 is expected to be one of the closest in recent history

The outgoing parliament, which has served a full five years, has been tarnished by a high-profile scandal over politicians' expenses.

As many as 150 MPs are stepping down, many with reputations harmed by the scandal.

Due to the scandal, some analysts expect fringe parties and independent candidates to pick up extra votes at the polls.

The Conservatives lead Labour in opinion polls but the gap has been narrowing.

A poll in Tuesday's Guardian newspaper showed Labour only four points behind the Conservatives, putting it on course to remain the largest party but without an overall majority.

Support for the Conservatives is unevenly distributed in Britain's 650 parliamentary constituencies, which means that Labour can win the most seats even if it does not capture the largest share of the vote nationally.

An inconclusive election result is rare in Britain and may rattle financial markets, which want a clear outcome and the promise of meaningful action to tackle a budget deficit running at almost 12 per cent of GDP.

Failure by either of the main parties to win a majority could hand a pivotal role to the smaller opposition Liberal Democrats, who will be trying to maintain a bloc of around 60 MPs in parliament.