Conservative MP Charles Walker has said he would quit the party if David Cameron strikes a deal with Nigel Farage in-order to stay in power after the election.
Ukip is hoping to get a handful of MPs elected to Westminster in May. Farage has said he expects to get at least ten. A Populus poll published today put Ukip in third place on 15% of the vote.
Farage has ruled out entering a formal coalition with any of the main parties, but has said he would support a minority government in exchange for a quick in/out EU referendum.
Speaking on the Daily Politics today, Walker, the MP for Broxbourne, said: "I wouldn't sit in an alliance with Ukip so whatever Ukip MP we gained I'd be off."
He added: "I'm not sitting in an alliance with Ukip as a Conservative MP, I'd rather sit as an independent Conservative MP than sit alongside Ukip."
Walker had was responding to Labour MP David Lammy, who said the prospect of a Conservative-Ukip deal should worry voters more than any Labour deal with the SNP.
Earlier today, Ed Balls said a coalition with the SNP after the May 7 general election is "not part of Labour's plans", but refused to rule it out. Balls and other senior figures within the party have come under increasing pressure to end speculation a pact may be on the cards, after polling suggesting the SNP is set to seize large numbers of seats from Labour north of the border.
David Cameron has said Ed Miliband should explicitly rule out a deal with the SNP "if he cares about this country", and Tories have released a poster showing the Labour leader in the pocket of former SNP leader Alex Salmond.
Asked if he could categorically rule out a deal with the nationalists, Balls said: "The SNP have said they don't want a coalition. It's not part of our plans. We don't want one, we don't need one, we're not after one.
"No large party in the last 100 years - Labour or Conservative - has ever fought a general election on the basis they wanted a coalition or deal with a small party. It's the last thing we want. What we want is a majority Labour government."