Gordon Brown is due to call the general election for May 6 – heralding the start of what is expected to be the hardest-fought campaign for many years.

The Prime Minister will seek an audience with the Queen, before returning to Downing Street to announce that the election campaign is under way.

Conservative leader David Cameron said he felt “good” about the election being called and it was “about time”.

Mr Cameron emerged from his London home at 6.30am with mugs of tea for waiting journalists before going for a jog. Asked how he felt about the election being called, he said: “I feel good. It’s about time. I’m getting fit for it.”

Parliament will be dissolved next Monday. But Mr Brown, accompanied by his wife Sarah, will immediately embark on a “GB On The Road” campaign based around direct contact with voters.

Heading initially to crucial seats in the South-East, the Prime Minister’s principal theme will be to warn voters that they cannot trust the Conservatives with the economy. Tory leader David Cameron will say that he is fighting to give hope to “the Great Ignored”.

With the election result more uncertain at this point in the campaign than at any election since 1992, the parties are digging in for what is likely to be a bitter slog to the end.

While two polls gave the Tories a 10-point lead – the kind of advantage they need to form a majority government – another suggested Labour were just four points behind. That would almost certainly result in a hung parliament and may even give Labour the most seats. Labour aides said on Monday night that they were fighting to win.

In a foretaste of Mr Brown’s campaign themes, he said: “The people of this country have fought too hard to get Britain on the road to recovery to allow anybody to take us back on the road to recession.”