6 May election battle set to commence

Gordon Brown is tonight preparing to fire the starting gun for the 2010 general election.

After months of anticipation, the Prime Minister is finally set to visit the Queen tomorrow to request the dissolution of Parliament for a 6 May election.

The month-long campaign promises to be the hardest fought for many years, with Labour and the Tories closer in the polls than at any general election since 1992.

Today's Bank Holiday - usually a relatively quiet day in the political calendar - was dominated by pre-election skirmishing between the party leaders.

After Mr Brown issued a podcast attacking the Tories' spending plans, shadow chancellor George Osborne unveiled a new Conservative poster accusing Labour of crushing the recovery.

Chancellor Alistair Darling took to the airwaves to defend next year's increase in National Insurance contributions - a move the Tories have promised to largely scrap.

The Conservatives today also released a Webcameron video on YouTube featuring Mr Cameron's pregnant wife, Samantha.

And Liberal Democrat leader Nick Clegg, a potential kingmaker in a hung parliament, unveiled one of his party's election battlebuses in North London today.

With the economy firmly centre stage for the campaign ahead, Mr Brown used his latest podcast on the Downing Street website to draw a comparison with Wayne Rooney's foot injury.

"After an injury you need support to recover, you need support to get back to match fitness, you need support to get back your full strength and then go on to lift the World Cup," he said.

"So with the economy - we're not back to full fitness, we need to maintain support.

"If we try and jump off the treatment table as if nothing had happened, we'll do more damage to the economy - and frankly that means we risk a double-dip recession. I think that's a risk we can't afford to take."

Mr Darling also attacked the Tories' plans to scrap his planned rise in NI, insisting it was an essential part of the deficit reduction package and would not cost jobs, as critics claim.

But Mr Osborne unveiled a new poster seeking to portray Labour stamping on the green shoots of recovery.

It showed a bleak landscape with just one green shoot emerging from the barren ground.

A boot bearing the words Jobs Tax - referring to the proposed NI increase - looms over the plant, as if about to crush it.

"The choice in this election is very, very clear," Mr Osborne said.

"You have either got Labour stamping out the recovery, stamping on the green shoots, or the Conservatives avoiding the jobs tax."

But the Tories also faced criticism over their promise to provide any cancer drugs that are licensed and have been recommended for a patient by their specialist.

The King's Fund thinktank said the Tory plan was effectively unfunded.

It is supposed to be covered by the money the NHS will save without having to pay increased NI to its staff, as it would under Labour.

But King's Fund chief economist Professor John Appleby said: "Of course that's not a real saving on today's budget.

"So the £200 million or so they say will be needed to fund these cancer drugs essentially has to come out of the current budget.

"That means stopping doing something else for other people."

He added: "It's a sleight of hand, to say the least, because the money isn't there to be saved yet, so the money will have to come out of existing budgets."

Mr Cameron later insisted the plan was funded, adding: "This cancer drugs vow will ensure more people get the drugs they need."

He was also featured with his wife in a new video, dubbed "Websamcameron" by the Tories, in which they refer to their expected fourth child.

Mrs Cameron takes a leading role in the video, talking to the camera about a visit the couple made to a youth club in East London last week.

In a sign of her growing role in the Conservative campaign, Mr Cameron is shown insisting she does not need any campaigning tips as she is a "natural" who is "eclipsing" him already.

Mrs Cameron responds that it is "the bump" - due in September - rather than herself that is so popular. Her husband says he can see it through her clothes already.

Meanwhile, the Prime Minister's difficulties with the unions increased as one leader described the Government as "the worst in the history of the country" for civil servants.

Mark Serwotka, general secretary of the Public and Commercial Services Union (PCS), accused Labour of being a poor employer.

Speaking at the National Union of Teachers' (NUT) annual conference in Liverpool, Mr Serwotka called on unions to "stand together" and take industrial action if necessary to defend jobs, pay and pensions.

He told delegates many union leaders have been arguing how well Labour has done, and that "we should be careful to appreciate what we've got".

But Mr Serwotka added: "I have to say to you this - that if you judge a government by how it behaves as an employer, this is the worst Government in the history of this country."