Boris Johnson has said he will "keep fudging" on whether or not he will stand to be an MP in 2015, to the frustration of an influential committee of Tory backbenchers.
Speculation has been mounting on whether the London mayor will return to parliament - and potentially succeed Cameron as leader of the Tories.
Appearing on Pienaar's Politics on Radio Five Live, Johnson was asked whether he would "keep fudging" on this issue and he replied "yes".
It has been reported Johnson will announce he will stand for a safe Tory seat in 2015 but pledge not to take a ministerial post while he serves out the remainder of his term as mayor, which ends in May 2016.
But backbench MPs have criticised his failure to confirm his plans.
Charles Walker, vice-chair of the 1922 Committee of Conservative MPs, told The Observer: "Boris needs to decide what he is doing. He needs to be decisive.
"Undoubtedly, he would be a great addition to parliament, but he needs to get on and decide what he is doing if he is to be taken seriously."
Many potential seats have been suggested for Johnson, including North West Hampshire, where Sir George Young has said he will stand down at the next election.