A major survey of everyone living in Brighton and Hove has been delayed because of a mix-up over envelopes.

A form asking people what they want if a directly-elected mayor is rejected, was sent to 100,000 homes, printed in the civic newspaper, City News.

But the pre-paid envelopes people were told to post their response in did not exist.

A spokesman for Brighton and Hove City Council said: "It was a mistake we unreservedly apologise for. We have had people ringing in about it and are very sorry for any confusion caused but we still need them to send us their forms."

The questionnaire asked people how the council should be run if they voted against a directly-elected mayor in a referendum likely to be held in October.

The wording was lifted from another leaflet about the referendum sent to 5,000 city residents, chosen at random from the electoral register.

The council spokesman said: "It was a cut and paste job. The words about the envelope were never meant to appear because we had never intended to provide a reply envelope.

"We always intended to foot the bill for the postage but did not give the correct instructions."

The date to return forms has now been put back two weeks, to May 25, and a freepost address has been set up.

Leader of the Liberal Democrats Coun Paul Elgood said: "We all make mistakes. However, this is a fairly significant one because I am concerned it may mar the outcome of the public consultation.

"This could create confusion and could put residents off stating their opinions.

The referendum was meant to be held on May 3. In February it was delayed after officers discovered it was possible to have a fallback proposal of the old-style committee structure if a directly-elected mayor was rejected.

Up until then, councillors believed they could not consider committees and had decided to continue with the current system of a leader and all-powerful Cabinet.

The questionnaire aims to find out which of the two systems residents would prefer if they rejected a directly-elected mayor.

Conservative group deputy leader Coun Brian Oxley said the response to the survey would have to be scrutinised in the light of the mistake.

He said: "Of course this is an oversight but many people may have not have bothered to reply when they could not find the envelope."

The results of the survey must be sent to the Government by June 30.

Corrected forms will appear in the Brighton and Hove leader on Friday. They and the original questionnaires in City News can be dropped in at any council building or sent to Policy and Communications, FREEPOST SEA2619, BN3 2ZZ.