Downing Street plays down Farage-Cameron debate reports
David Cameron has "not ruled anything in or out" when it came to televised debates ahead of next year's general election, Downing Street said.
But a spokesman dismissed reports the prime minister was willing to include UKIP leader Nigel Farage in one of them as "speculation".
Tory chairman Grant Shapps said talks on the format and timing of any debates would start in the autumn.
Labour have accused the Tories of dragging their heels on the issue.
According to The Sunday Times, Mr Cameron is open to the idea of taking part in a debate with Mr Farage, as part of a "2-3-5" format drawn up by his aides.
Under the plan, Mr Cameron would hold one head-to-head debate with Labour leader Ed Miliband - as the other potential prime minister - a second, which would also include Liberal Democrat leader Nick Clegg, and a third with Mr Farage and the Green party leader Natalie Bennett.
Mr Shapps told Sky News "all options are on the table right now" but talks would have to wait until "the back of this year".
"We think the debates were a good innovation, they were something new at the last general election," he said.
"There was a bit of a problem they all took place during the general election, people across the country didn't get to see the party leaders and the debate properly in their local area.
"It's quite possible not to bunch them up in a campaign now we know the election date is 7 May."
The Sunday Times suggested one of the debates would be held during the campaign, with the others beforehand.
But a Downing Street source said: "It is speculation on what might happen in talks that are not going to happen for several months.
"We have not ruled anything in or out, so that means people can speculate what might happen in the talks.
"But the reality is these talks are several months away."
Last month, Ed Miliband said the 2010 format of three debates between the three main party leaders over three weeks should be a "starting point" but that he was open to moves such as a less formal setting and greater voter participation.
In an article for The Radio Times, he called for immediate negotiations, accusing Mr Cameron of being the "single biggest obstacle" to them going ahead.
Quizzed earlier on The Andrew Marr Show about whether he would take part in a debate with Nigel Farage, he said it was "up to the broadcasters who they invite, whether they invite Nigel".
He said: "My main desire is that the debates go ahead. The prime minister doesn't own these debates, the British people own these debates and he can't wriggle out of them."
Mr Farage, who locked horns with Mr Miliband over an EU referendum on the programme, said: "What David Cameron does, very often he makes these promises, vague promises, and then doesn't actually deliver afterwards.
"I don't think he has got any intention of allowing me into any of these debates."
Opinion polls suggested Mr Farage beat Lib Dem leader Nick Clegg in two debates ahead of this month's European elections.