Ukip leader Nigel Farage has repeatedly challenged the Prime Minister to a televised debate.
His most recent call to face Cameron on air came last week in response to claims he was "chicken" for ruling out a run at Parliament in the Newark by-election.
The Ukip leader said: "Mr Cameron said ... that I was a chicken. Well, I'll tell you what Dave, why don't you come on telly and do a debate with me?"
More top news
Internet search engine says Cilla Black was the subject of more online searches than Kim Kardashian this year, beaten only by Taylor Swift.
A supermarket price war and fierce competition across the rest of the high street has seen shop prices slumped by a record level last month.
The PM urged Tory MPs not to side with Jeremy Corbyn by opposing British airstrikes against Islamic State in Syria, ahead of a Commons vote.