Ministers will ask Birmingham whether it wants a directly-elected mayor or not without revealing what powers a mayor will receive, the Government has admitted.
No decision will be taken on devolving powers to a new city mayor until after they have been elected.
Birmingham is to hold a referendum on May 3 on whether to replace the existing system of local government with a new high profile mayor.
But residents will be in the dark about the powers a mayor will actually enjoy - one of the key issues likely to come up in the referendum campaign.
Ministers have hinted that a mayor could take control of public transport, skills and training and economic development.
Other proposals include letting a mayor help set the curriculum in city schools, to ensure children are taught the skills local employers need, or overseeing the work of West Midlands Police.
But in a statement to the House of Commons, Local Government Minister Greg Clark said the Government would simply wait until after a mayor had been elected, and then ask them what powers they thought they should have.
It follows a three-month consultation with city councils and other public bodies, which appears to have failed to reach any conclusions.
Mr Clark said: “Where a mayor is elected we would expect that mayor to come forward with his or her own request for the powers they seek to take.”
He added: “Each one of our great cities is unique, with different needs, characteristics and ambitions. The Localism Act allows the Government to devolve the powers to any city that the city requests and that is the approach that we will take to new mayors.”
Birmingham and Coventry are both to hold referendums in May on creating a mayor. If residents vote “yes” then an election may be held in November this year.
Possible candidates to become mayor of Birmingham so far include former Labour MP Sion Simon, Labour MP Gisela Stuart (Lab Edgbaston) and former city council leader Sir Albert Bore.