No 10 signs up Boris's campaign manager

Crosby: street-fighter reputation (AP)

David Cameron has hired Boris Johnson's controversial polling guru in an attempt to keep the Tories in power beyond the next general election, in 2015, it emerged last night.

The Australian political consultant Lynton Crosby will return to a key role in Conservative headquarters to help plot the party's re-election strategy, starting in the New Year. He is expected to start on a part-time basis and then become full time as the next election approaches.

The move comes in the wake of the party's defeat in last week's Corby by-election, when Labour overturned a 1,900-vote Tory majority to win by more than 7,700. The UK Independence Party came third with more than 5,100 votes. The rehiring of Mr Crosby, who led the Tory campaign in 2005, will increase speculation that the Chancellor will relinquish control of election planning.

Mr Crosby is a legendary political "street-fighter" who has been credited with inspiring a series of right-wing victories in Australia and the UK over the past two decades. After helping out on the victorious campaigns of the former Australian premier John Howard, he ran Mr Johnson's successful campaigns to become Mayor of London in 2008 and 2012.

Earlier this month, the Mayor told Tory MPs the party would be "mad" not to hire Mr Crosby for the 2015 general election and said they should pay him whatever salary it took. "They should kill the fatted calf, break the piggy bank, go for Lynton but give him a pretty free hand to run things," Mr Johnson added. "He will be demonised by the media as some sort of attack dog."