Robert Kilroy-Silk has confirmed he wants to be the leader of UKIP but says there is no mechanism for him to run against current leader Roger Knapman.
Mr Kilroy-Silk said he had the support of senior party members
The MEP told the BBC's Breakfast with Frost programme he believed he had the support of every senior member of UKIP.
Mr Kilroy-Silk said Mr Knapman had told him he wanted to stand down after the 10 June European elections.
But Mr Knapman, speaking to BBC News 24, rubbished the claims and said he had no intention of stepping down.
Explaining how the party's unexpected gains in June had changed his plans, Mr Kilroy-Silk said: "But then of course he [Mr Knapman] got a massive election result and probably he liked the size of his new train set."
But Mr Knapman said: "It is not within my grasp to come to such a deal and indeed such a deal was never come to or even discussed."
UKIP, which favours withdrawal from the EU, has just reversed its position on not standing against eurosceptic Tory MPs at its party conference in Bristol.
Mr Kilroy-Silk, a former Labour MP and chat show host, told delegates the Conservative Party was dying and the UK Independence Party must replace it.
The East Midlands MEP accused the Tories of stealing UKIP policies on immigration.
And he said Prime Minister Tony Blair was "living in fantasy land".
UKIP delegates debated the idea of not fielding candidates in areas where sitting Conservative MPs backed its anti-Euro stance.
But an overwhelming majority voted to put up candidates in every constituency at the general election.
The party has been buoyed by its third place in Thursday's Hartlepool by-election, pushing the Tories into fourth place.
Earlier, Mr Kilroy-Silk told the conference there must be no deal between UKIP and the Tories.
He said: "The Conservative Party is dying. Why would you want to give it the kiss of life?
"What we have to do is kill it."
Mr Kilroy-Silk, whose speech focused on immigration and asylum, said UKIP had "upset the political apple cart" and "could change the face of British politics forever".