Two Birmingham MPs are setting aside their party political differences to campaign against the city council being run by a directly elected mayor.

Liberal Democrat John Hemming and Labour’s Roger Godsiff are “testing the water” to see whether enough support exists to run a No campaign in the run-up to next May’s referendum when 750,000 voters across Birmingham will decide whether they want a mayor.

Mr Hemming, who has contacted all 120 city councillors, said initial reaction made it very likely that a formal organisation will be formed soon.

Although no decisions have been taken, the campaign is likely to be supported by all of the main political parties and based around a slogan with a working title of Say No to an Elected Dictator, Mr Hemming said.

Ironically, if he succeeds in keeping the existing system, where the council is run by a leader and cabinet, Mr Hemming could be doing himself out of a job.

Although he has always been opposed to mayors, he has said that he would probably put himself forward as the Liberal Democrat candidate for the office if Birmingham does vote to have a mayoral election in May 2013.

Mr Hemming, the MP for Yardley, was instrumental in helping to lead a successful anti-mayor campaign 10 years ago. As a city councillor in 2001, he joined forces with Mike Whitby, now the Tory leader of Birmingham City Council, to publicise the case against a mayor.

Then, as now, the campaign was based on a claim that the mayor would have too much power and be a virtual dictator.

A consultative ballot saw an overall majority of votes cast for one of two different types of mayor. But the single largest proportion of votes was in favour of continuing with a council leader and cabinet, prompting the Government to tell Birmingham it need not have a mayor.

This time around, Mr Hemming may face more of a struggle to get the no vote out.

City mayors have been backed strongly by David Cameron, the Prime Minister, and the Birmingham referendum will take place at the end of what is likely to be a lively election contest in London between Tory mayor Boris Johnson and Labour’s Ken Livingstone.

Supporters of change expect that publicity generated by the Boris-Ken tussle will create new public interest in the city mayor system, pushing up the yes vote in Birmingham, Coventry and other English cities where referendums are being held.

Mr Hemming said: “The point about directly elected mayors is that they have four years of complete power. The only constraint is that they have to get one-third of the council to back their budget every year.”