Mr Robinson said the council wished more questions could be asked
Campaigners calling for a "third choice" in a referendum on Stoke-on-Trent's political system would need a law change, a council boss said.
The city council will decide if it wants a council leader and cabinet or an elected mayor and cabinet and then ask voters if they support its choice.
City council head Steve Robinson said the law was "very clear" these were only two choices for local government.
Opponents say 2,000 people have signed a petition calling for more choice.
The council has been told it must introduce a new political system by May 2009 and a referendum could be held in October.
The council is the only authority in England to have a mayor and council manager and a government commission reported in May that residents were being "short-changed" because the present set-up was not working.
Mr Robinson, chief executive of Stoke-on-Trent City Council, said he understood why the subject was proving controversial, but legislation was clear that only an elected mayor and cabinet or a leader and cabinet could be offered.
"You can have a view whether there should be more but that's what government is saying about local government.
"It applies to every council in the land."
He added that the council would like to be able to pose more questions to the public, but that would not be a referendum.
"I think what is difficult here is that there's only one question we can put to the electorate and that is not the best way," he said.
"We would much prefer to have a question that gave people a choice but unfortunately when you look at the details of the legislation that's not legislation, that's a poll."
Concern was also raised when it was revealed last month that Stoke-on-Trent could keep an elected mayor even if the public votes against one.
A council report said a barrister had advised that the fallback option would be an elected mayor and cabinet system.