Election: Vote battle intensifies for final three days
Cameron denies he is 'over-confident'
Gordon Brown, David Cameron and Nick Clegg have been blitzing key seats, as they target the millions of people they say have not yet decided how to vote.
In the final three days of campaigning polls put the Tories ahead but not by enough to get a majority.
Mr Cameron says his party will campaign through the night on Tuesday, Mr Brown vowed to fight "every inch" of the way.
Mr Clegg told supporters in south east London "the sky's the limit" and they had "three days to change Britain".
The three leaders are spending the bank holiday visiting numerous seats they hope to win on 6 May.
The BBC's Political Editor Nick Robinson said their focus was on the huge number of voters yet to make up their minds with Gordon Brown aware that - as the opinion polls stand at the moment - he may not be returning to Downing Street as prime minister.
Three days before the closest election since 1992, an ICM/Guardian poll puts the Conservatives on 33%, Labour and the Lib Dems on 28% while a YouGov poll for the Sun puts the Tories on 34%, Lib Dems on 29% and Labour on 28% - which continue to point to a hung parliament.
But an Ipsos MORI poll of 57 marginal seats for Reuters out on Monday suggests the Conservatives could win an outright majority - of just two seats.
In Blackpool, Mr Cameron said there was not "one ounce of complacency" in his campaign and pledged a through-the-night campaign from Tuesday night to Wednesday night, meeting people who work in the early hours like fishermen, bakers and florists.
In this country you don't inherit power, you have to earn it
He said he was taking "no vote for granted" and recognised that "millions" of people were still making up their minds.
In a message to his parliamentary candidates he said: "This is the vital time. You need to go door to door, street to street, house to house. We have a huge amount of work to do, a lot of people left to convince.
"If we get out there we can... win it and win it for our country."
Later he was joined by London mayor Boris Johnson and Olympic gold medal winner rower James Cracknell in Southwark, south London, to talk about his plans for a "schools' Olympics".
But Labour's Lord Mandelson said Mr Cameron was "preparing to waltz into Downing Street" but said "two thirds of voters or thereabouts are not dancing to the Tories' tune". Labour ministers lined up to attack the Conservatives over child tax credits.
Labour's election co-ordinator Douglas Alexander also recognised there were an "unprecedented number of people who still have to make up their minds".
Mr Brown has been to Basildon, Ipswich and Great Yarmouth on Monday accompanied by Dragons' Den entrepreneur Duncan Bannatyne.
Meeting staff at a parcel delivery firm in Basildon, he said: "I am the most optimistic man in Britain, because I have got a plan for the future."
But he acknowledged he was "fighting for my life" in what he described as "a post global-financial-crisis election".
He said: "I'm going to fight every inch of the way and every second of the day to tell people in Britain that fight for the future must mean people look at our plan and what we're proposing."
Meanwhile, addressing supporters in Blackheath, south-east London, Mr Clegg accused Mr Cameron of "breathtaking arrogance" and of "measuring up the curtains" at 10 Downing Street before the election had taken place.
Urging activists to "campaign every minute of the day", he said: "Anything can happen. The sky's the limit."
Brown: 'I'm fighting for the future
Mr Clegg said: "We have got three days in this most exciting election campaign, three days to change Britain for good. Three days to deliver the fairness... for the families and communities of Great Britain."
He acknowledged a change in Lib Dem strategy - campaigning in seats like Streatham and Lewisham that the party would not have expected to win. Mr Clegg told the BBC: "We are reaching deeper into parts of Britain that have been let down by Labour in particular for so long."
The Lib Dems have also released a list of celebrity supporters - which includes actors Colin Firth and Harry Potter star Daniel Radcliffe, satirist Armando Ianucci and campaigner Bianca Jagger.
The Conservatives have unveiled plans for a "contract for young people", to guarantee them help with training and getting jobs, while Labour have published a "seaside manifesto" to boost resort towns and help them benefit from economic regeneration.
The three leaders also addressed, in succession, a Citizens UK election "assembly" of about 2,500 people in London, each outlining their proposals for supporting voluntary and community organisations.
All three backed, in principle, the concept of a "living wage" of more than £7 an hour for low-paid public sector workers.
Mr Cameron said it was "an idea whose time has come", adding that he wanted to see his "big society" philosophy of community involvement in public services "marching down the corridors of Whitehall".
Following him, Mr Clegg said he supported a cap on interest rates charged on credit cards, store cards and unsecured loans.
He also defended his plan for a one-off "amnesty" for illegal immigrants who have lived in the UK for 10 years, saying the "only people who have anything to fear" from the proposal were "evil criminals" exploiting such people.
Bringing the event to a close, Gordon Brown said the fight for "justice for the low-paid" must continue, stressing the minimum wage itself would rise to £7 by about 2014.
Before he had spoken he had comforted a girl who wept as she tried to tell the event about how her family struggled on their wages.
Tiari Sanchez, 14, from west London, said her family would eat lentils for a week because they had so little money.
Her mother Sandra and grandmother Marta Rozas, 62, work 40 hours a week as cleaners in the Treasury for £6.95 an hour.
Matthew Bolton, who heads the living wage campaign, said Mr Brown had told him that "regardless of what happens on Thursday" he wanted to meet with the family.
Mr Brown, whose speech was briefly interrupted by an anti-nuclear protester, also said Labour would turn the Post Office into a people's bank so that no-one was more than a "few miles away" from affordable banking services.
Also out on the campaign trail, former Prime Minister Tony Blair attacked Lib Dem policies, saying: "This Clegg business is absurd."
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