Party leaders off and running in race for No 10

Gordon Brown launched the General Election campaign today with an appeal to the country to give him "a clear and straightforward mandate" to continue the work of economic recovery.

The Prime Minister emerged from No 10 Downing Street shortly before 11am to confirm what he described as "the least well-kept secret of recent years" - that the country would go to the polls on May 6.

Tory leader David Cameron said it would be "the most important General Election for a generation", while Liberal Democrat leader Nick Clegg said it marked "the beginning of the end" for Mr Brown.

In apparent anticipation of a possible hung parliament, Downing Street announced the new parliament would not meet until May 18, allowing 12 days for potential horse-trading among the parties over the formation of a new government.

Mr Brown made clear he intended to make the economy the centrepiece of his campaign - holding out the prospect of a return to prosperity under Labour while warning of rising unemployment and business failures under the Conservatives.

Flanked by his entire Cabinet outside the door of No 10, he warned that failure to get right the "big decisions" on the economy over the next few months risked tipping the country back into a "double-dip" recession.

"Over the next few weeks I will go round the country - the length and breadth of our land - and I will 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," he said.

"Get the big decisions right - as we did in the last 18 months since the world recession - and jobs, prosperity and better standards of living will result. Get the big decisions wrong and the lives of hundreds of thousands of people are diminished as a result."

"That is why I am asking the British people - I'm asking you, the British people - for a clear and straightforward mandate to continue the urgent and hard work securing the recovery."

Mr Brown, who described himself as a man from "an ordinary middle class family in an ordinary town" who still lived by the values instilled in him by his parents, also promised a "comprehensive plan" to clean up politics in the wake of the expenses scandal.

Even before the Prime Minister had made the formal announcement of the election date, Mr Cameron had kicked off his own campaign with an appearance before supporters in front of London's County Hall, just over the river from No 10.

Against the backdrop of Westminster Bridge and the Houses of Parliament, the Conservative leader said that they would fight on a message of "hope, optimism and change".

"This country deserves a lot better than five more years of Gordon Brown and that is what we must offer," he said.

"So let's get out there and say 'Let's get off this road to ruin and instead get on the path to prosperity and progress'.

"Let's fight for what we believe in. Let's take the case to the country, to the people of this country, about hope, optimism and change."

Meanwhile Mr Clegg, addressing activists at the Lib Dems' Westminster headquarters, insisted that it was not simply a two-way fight between the two biggest parties.

"This isn't the old politics of a two-horse race between Labour and the Conservative Party," he said.

"The real choice is between the old politics of Labour and Conservatives and something different, something new and that is what we offer."

"This is a huge, huge election. It is certainly the beginning of the end for Brown, that's for sure."

Following the announcement of the election date, all three leaders headed off to campaign around the country with Mr Brown going to Kent, Mr Cameron the Midlands and the North, and Mr Clegg Watford.

The Prime Minister began the day with a final meeting of the Cabinet before leaving Downing Street at 10am for the short drive to Buckingham Palace to seek the formal dissolution of parliament.

The Queen, who is currently in residence at Windsor Castle, was flown in by helicopter in order to meet him.

The rest of the week will be devoted to the parliamentary "wash-up", as the Government haggles with the opposition parties to try to get as much of its outstanding legislation on to the Statute Book.

Parliament will then be dissolved on Monday marking the official start of the campaign.