Nigel Farage has said his party is open to deals with the Tories, where Ukip candidates stand aside in seats where Conservative Eurosceptics are standing.
The Ukip leader has ruled out a formal electoral pact, but suggested he would not stand in the way of agreements made at constituency level.
Negotiations may prove tricky however, after Foreign Secretary William Hague insisted Tories "don't make pacts with other parties" and instead issued a caution to wavering supporters that they risked letting Labour into power.
A number of high-profile Conservatives have floated the possibility of an alliance with Ukip in the run-up to the election to avoid splitting the right-wing vote, including Jacob Rees-Mogg who suggested that Farage's party would expect to get some MPs out of any deal.
Writing in The Times Farage said: "If either they, or others like them, even Labour MPs, with their local associations, chose to propose running on a joint ticket then I would leave the local Ukip association to have those associations.
"If after discussions they feel that it would be a better way to serve their constituents, then I and the National Executive Committee would be happy to hear reasoning. After all we are a party that believes in real localism and doesn't think that the centre is the repository of all wisdom."
A ComRes survey found 22% of Tory local councillors supported a pact but Hague told Pienaar's Politics on BBC Radio 5 Live: "I do rule that out."
"We don't make electoral pacts with other parties; we do make pacts with the voters of other parties and win over the voters of other parties as we've often done through history.
"And, of course, if someone is contemplating voting Ukip who would otherwise vote Conservative they could, by default, produce a Labour government which is the absolute opposite of what they might want on Europe for instance.
"They might be voting for Ukip because they want to have a referendum on Europe. Well, they are only going to get that if David Cameron is prime minister after the next election.
"Whatever they have done in local elections or whatever they say in opinion polls, at the next general election a voter like that will have to choose: are they going to have Ed Miliband as prime minister and go headlong into giving away more of the country's powers or are they going to have a referendum under David Cameron?
"A general election in this country is a first-past-the-post system. It is a choice."
Party chiefs were accused of trying to "stifle debate" on the issue after an advert for a fringe meeting featuring Farage failed to appear in the official conference guide.
The Ukip leader is tipped to draw a big crowd after being invited to speak at an event organised by the Thatcherite Bruges Group at Manchester town hall - one of the largest conference venues.
But despite having its £250 payment for a plug for the meeting accepted, the group - named for Baroness Thatcher's speech about a European "super state" - was told the ad had been pulled.
Bruges Group director Robert Oulds said: "It is wrong that they are trying to hide this meeting from party members at the conference.
"I am concerned that the party may be trying to stifle debate on this subject.
"Instead of ignoring the problem, we have to start to have a debate and to understand each other."