There will be a second election by Christmas if David Cameron or Ed Miliband attempt to go it alone with a "messy and unstable" minority administration, Nick Clegg has warned.
The Liberal Democrat leader said a minority government, relying on the support of either UKIP or the SNP, would be chaotic and the two main party leaders should not put their own interests ahead of those of the British people.
Mr Clegg, who is travelling the country in a 1,000-mile, 30-hour tourwith two days until polls open, said: "The last thing Britain needs is a second election before Christmas.
"But that is exactly what will happen if Ed Miliband and David Cameron put their own political interest ahead of the national interest."
He claimed a coalition with the Liberal Democrats was the only way to ensure a "stable" government.
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On a visit to Cardiff he said: "Everybody knows that no-one will win this election - even if David Cameron and Ed Miliband won't admit it publicly.
"That means that politicians will have to work together to put the country first.
"The Liberal Democrats have shown that coalitions can be strong and stable. But instead of creating stability, Labour and the Conservatives will create a shambles."
The Lib Dems enjoyed a two-point jump in a YouGov/The Sun poll this morning, putting the Lib Dems on 10%.
The latest Sky News poll of polls has the Conservative and Labour parties tied on 33% and a projection suggests Mr Cameron's party would win 277 seats, Labour 275, Liberal Democrats 18, UKIP 2, SNP 55 and others 23.
Because of the Fixed-term Parliament Act a second election could only be called if there was a specific vote of no confidence in the government or if two-thirds of the House of Commons voted for one.
On the campaign trail today both Mr Cameron and Mr Miliband continued to insist they can win a majority, despite the polls consistently suggesting a hung parliament.
Mr Cameron says the party only needs 23 seats to win the election and Mr Miliband has insisted he is "fighting for every vote".
The Labour leader sought to play down suggestions that senior figures in his party were considering a minority government with the Liberal Democrats.
He said: "I am not going to start talking about politicians and what they start doing on Friday, I am going to talk about what the British people do on Thursday."
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During a visit to a garden centre in Twickenham, Mr Cameron was heckled by an SNP supporter who accused the party of drumming up racism with their comments about Labour doing a deal with Nicola Sturgeon's party.
As Mr Cameron was speaking, the man shouted: "Come on SNP. Is there going to be an ajockalypse? I'm from Scotland - the racism I'm getting because of these people and Boris. It's not fair. Come on SNP."
He was led away.
A clearly energised Mr Cameron, who has previously faced criticism for a lacklustre campaign, told the crowd: "I feel like the firefighter hosing down the burning building and there's Ed Miliband the arsonist saying why aren't you doing it quicker - that's how I feel, that's why we need five more years."
Mr Cameron was later challenged by a worker during a visit to an internet firm in Hendon, north London, with Boris Johnson, who is running for MP in Uxbridge, west London.
He was told people were disaffected because the Prime Minister, his Chancellor and Mr Johnson had all gone to the "same school" and had been "dismantling the country's assets" for reasons of "self interest".
