Media playback is unsupported on your device Media caption Boris Johnson jokes about being PM and mayor

David Cameron has said he believes Boris Johnson could return to the House of Commons in 2015 and that the two "can make a very good team".

Asked about the Mayor of London's future, the prime minister told BBC Radio 4's Today: "I think he's got an enormous amount to give to public life.

"I don't think he's given up on that idea either. So... we're quite well aligned, if I can put it that way."

Mr Johnson has urged activists to work "flat out" for a Tory victory in 2015.

In his speech to the conference, Mr Johnson made no direct reference to his future.

But he remarked that French politician Alain Juppe had been Mayor of Bordeaux while he was French prime minister, joking that this was a "good idea".

'Massive asset'

Mr Johnson has ruled out standing for a third term as London mayor and suggested that something will "crop up" when his time in office ends in 2016.

Some Tories have urged him to consider standing for Parliament in 2015, citing the precedent of Ken Livingstone who remained an MP during his first year as mayor.

Mr Johnson has long been regarded as a rival to Mr Cameron but the BBC News Channel's Norman Smith said he was maintaining a lower profile at conference this year to avoid being accused of stealing the limelight from the prime minister.

Mr Cameron said the mayor of London was a "massive asset" to his party and the country and suggested there could be a job for him in a future Conservative government.

"My message to him is that you are a brilliant mayor, you have done a great job, you have a lot more to give to public life and it would be great to have you back in the House of Commons at some stage contributing to public life. But that is up to him."

'Warm welcome'

Asked whether he could envisage a return as soon as 2015, the PM said "absolutely" and stressed he would give him a "very warm welcome".

"It is a matter for him, it is his plan. All I know is that... we can make a very strong team together, we do today."

Sources close to the mayor of London have said he has not applied to be the Conservative candidate for the seat of Croydon South, where the sitting MP is retiring.

In his speech, Mr Johnson praised the prime minister as the "only statesman in the European Union" capable of delivering reform and a referendum for the British people.

He said the choice at the next election was between the "fools gold" offered by Labour and a Conservative Party which had taken "difficult and sensible" decisions - urging his party to remove "the Liberal Democrat albatross from around our necks" and push for outright victory.

But he urged David Cameron to reconsider stamp duty levels in London and elsewhere, saying it was having a "baleful effect" on aspiring home owners.

The tax was "stamping on the fingers of those trying to get on the property ladder", he added.