An election lawyer has claimed that the mayoral referendum in Birmingham could be open to legal challenge after three important words were missing from official information leaflets.

The Birmingham City Council leaflets, delivered to all 400,000 homes in Birmingham have printed only part of the question that will be asked on the referendum ballot paper on May 3.

The council leaflet read: “How would you like Birmingham City Council to be run?

By a Leader who is an elected councillor chosen by the other elected councillors. This is how the Council is run now.

- or -

By a Mayor who is elected by voters. This would be a change from how the Council is run now."

But it should have read: “By a Leader who is an elected councillor chosen by a vote of the other elected councillors.”

At least three councils, Birmingham, Newcastle and Wakefield have missed out the three words on information material.

Lawyer Ros Baston, who used to work for the Electoral Commission, said the omission of the three words made the council leader option seem slightly less democratic, as if the leader had been appointed at a secret meeting of councillors.

However, she recognised that this may go on anyway inside political group meetings before the leader was appointed in a public vote.

She said: “It doesn’t seem like much, but the Electoral Commission tested the question and saw how people reacted to it. But they felt having the extra words enabled people to make an informed choice.”

She added that the potential for a legal challenge would depend on how close the referendum result is.

Yardley MP John Hemming, a leader of Birmingham’s official No to an elected mayor campaign, said he did not suspect foul play.

“It is probably just a typo. I am not reading anything into it,” he said.

A City Council spokesman said the leaflet had been checked with the Department for Communities and Local Government to ensure it met regulations.