The wife of a Liberal Democrat candidate has been arrested by detectives investigating potential vote-rigging at next week's local elections in Birmingham.

The arrest of the 50 year-old wife of Mohammed Khan, who is standing as the Lib Dem candidate in the Nechells ward, came as police recovered a quantity of postal voting forms at an address in Ronald Road, Bordesley Green. Other material was found by officers specialising in preventing potential electoral fraud during another search at a house in neighbouring Hob Moor Road.

The woman was arrested on suspicion of conspiracy to defraud the local election process. She was later released on police bail.

According to the latest electoral register, 17 people are listed at the property in Ronald Road and 12 at Hob Moor Road. Nine of those at the latter address have identical names to those at Ronald Road.

Det Insp Simon Wallis, from the West Midlands Police Economic Crime Unit, said: "There are other persons yet to be spoken to in connection with this matter. We are working closely with Birmingham City Council to seek to make the election process a fair, fraud-free process. We are vigilant to signs of fraud and intent upon taking positive action where appropriate."

Coun Paul Tilsley (Lib Dem Sheldon), deputy leader of Birmingham City Council and leader of the Liberal Democrat Group said: "We are carrying out our own investigation because a person has been arrested.

"We understand it relates to 11 votes at one house which were properly registered and until we can confirm this there is nothing more I can say.

"The Liberal Democrats both nationally and locally are totally opposed to any misuse of the system. If anyone is found guilty appropriate action will be taken."

Electoral officials in Birmingham are keen to avoid a repeat of allegations of postal vote fraud which surrounded the local elections in June 2004. A subsequent Election Court hearing, headed by Election Commissioner Richard Mawrey QC, found that the ballot-rigging perpetrated in two Birmingham wards would have disgraced a banana republic."

Mr Mawrey - who called for changes in the postal voting system to prevent future abuses - ruled that thousands of votes had been forged, stolen or otherwise tampered with.

Commenting on news of the 50-year-old woman's arrest, Birmingham Returning Officer Steven Hughes said: "We have been and continue to work closely with the police to prevent and tackle electoral fraud."

This year Birmingham City Council has issued 58,962 postal voting forms, a decrease of more than 10,000 on the 2004 figure.

Councillor Ian Ward, deputy leader of the Labour group at Birmingham City Council, said: "This reinforces why we were asking for tighter controls around postal votes but the other parties would not agree to it, which is unfortunate."

An Electoral Commission spokeswoman said: "The Electoral Commission has no powers to investigate allegations of fraud. That responsibility lies with the police.

"We are pleased that the police are treating allegations of fraud with the seriousness that a criminal offence merits.

"Whereas your bobby on the beat may have not known what to do in the past if you said your vote has been stolen, people are now being caught and convicted."