The leader of the Liberal Democrat Party has ruled out a coalition with Labour that relied on "life support" from the Scottish National Party (SNP).
Nick Clegg told the Financial Times that any coalition with an party that did not have the most votes would lack "legitimacy" with voters, who would question its "birthright".
He said: "I totally rule out any arrangements with the SNP — in the same way I rule out any arrangements with Ukip — because there is no meeting point for me with one party that basically wants to pull our country to bits and another party that wants us to pull out of the EU.
"I would never recommend to the Liberal Democrats that we help establish a government which is basically on a life support system, where [former SNP leader] Alex Salmond could pull the plug any time he wants. No, no, no."
In the event of a hung parliament after the 7 May election, Clegg said that he would first negotiate with the leader of the largest party, which if the polls are correct is likely to be David Cameron's Conservatives.
However, he added, if those talks failed he would then, reluctantly, talk to the leader of the smaller party in the Commons. He fears, though, that any so-called "coalition of the losers" could lack "legitimacy".
"You cannot provide stability, you can't take difficult decisions, if people are constantly questioning the birthright of a government," he said.
Clegg was also scathing of what he called the Conservatives' "socially regressive" plans for spending cuts and their "obsession" with Europe, which he claimed undermined Britain's influence in the world.
Meanwhile, the SNP expects to wield "enormous influence" over Labour if the party forms a minority government, party leader and Scottish First Minister Nicola Sturgeon has admitted.
In an interview with The Times, she sought to allay English voters' fears of a "mess" if Miliband had to rely on SNP votes, and thanked Cameron for boosting her party's position.
She said: "I know how minority government works. You have influence — particularly with the Fixed Term Parliament Act, you can change the direction of a government or defeat it on particular issues without the government falling and there being a general election. That gives enormous influence to a smaller party in opposition."
She added: "I am not going into all the tactics we would use to try to exert influence but suffice to say in that scenario there is considerable influence a minority party could wield."