DAVID Cameron has brushed aside the possibility of a Tory plot against him, but a potential future rival has received another political boost.

As the Prime Minister shrugged off suggestions that up to 14 Conservative MPs had signed letters calling for a change of leader, a poll showed Boris Johnson was continuing to enjoy an Olympic bounce.

A YouGov survey of 1700 people showed a "respect" rating of +25 for Mr Johnson compared to -18 for Mr Cameron and -53 for George Osborne, the London Mayor's possible rival in any future leadership contest.

Not surprisingly, Mr Johnson's strongest support was in the south of England and his weakest was in Scotland.

This latest snapshot follows an earlier poll this week that found the Tories would rise six points if the London Mayor replaced the Prime Minister as the leader of their party.

The mutterings of a future challenge to Mr Cameron's leadership are unlikely to diminish as next month's Conservative gathering in Birmingham month nears.

One of the conference highlights is Mr Johnson's set-piece speech. On the back of the success of the Games, he is expected to be given a rousing reception.

Party conferences are renowned as breeding grounds for rebellion and expressions of discontent with the leadership.

There already seems to be a lack of fear if not boldness on the back benches to question Mr Cameron.

Recent developments have included: Tim Yeo's "man or mouse" challenge over a third Heathrow runway; Brian Binley likening the PM to Nick Clegg's "chambermaid"; Bob Stewart being approached to launch a stalking horse challenge to Mr Cameron; the launch of Conservative Voice led by Liam Fox and David Davis, presenting a right-wing alternative agenda on tax, welfare and Europe; and up to 14 MPs signing letters calling for a leadership challenge.

While to initiate such a challenge requires 46 signatories, the fact there is a group of anti-Camerons operating at Westminster will be a warning to the PM that the run-in to the next General Election might not be as smooth as he'd like.