He said yesterday that Britain's "potty" electoral system meant it was possible Labour could get fewer votes than both the Lib Dems and the Conservatives on May 6 and still emerge as the biggest party in a hung parliament.
In an interview with BBC1's The Andrew Marr Show, Mr Clegg, pictured, made clear that there was no question in those circumstances of the Lib Dems combining with Labour to enable Gordon Brown to hang on to power.
"It is just preposterous the idea that if a party comes third in the number of votes, it still has somehow the right to carry on squatting in No 10," he said.
"I think a party which has come third – and so millions of people have decided to abandon them – has lost the election spectacularly (and) cannot then lay claim to providing the prime minister of this country."
Mr Clegg indicated that whatever the outcome of the election, he would have to consult his party before entering a coalition with another party.
"Any leader worth their salt would of course seek to bring their party along with them and I would do that," he said.
He said that he believed that whoever formed the next government would have to accept that reform of the electoral system – long a key Lib Dem demand – was now inevitable.
"You cannot now duck the fact that we have an electoral system which is completely out of step with the aspirations and hopes of millions of British people," he said. "A political system can't survive for very long if it is that out of whack with the rest of the country that it is supposed to be representing."