A fraud investigation was launched after an Oxford University student complained his signature was forged on local election nomination papers.

Christian Langkamp, a student at Lincoln College, discovered his name had been used to nominate Conservative candidates for the May 2 poll in Carfax ward.

He complained to the city council's returning officer, Martin John, that his name had been forged to nominate Anne Dykes and Stephen Pritchard.

Neither candidate won a seat, but if they had done so and forgery was proved, it would have prompted a by-election.

Mr John started to investigate the offence under the Local Government Act 2000, but when Mr Langkamp - who is a member of Oxford University Conservative Association - discovered the culprit could receive a six-month prison sentence he withdrew his complaint.

Mr Langkamp said: "I don't want anyone branded."

He is now demanding that there is no repetition in subsequent elections. Returning officer Martin John said Mr Langkamp told him that he would have offered to sign the Tory nominations, but no-one had asked his permission.

Mr John said: "Mr Langkamp made a formal complaint and then shortly afterwards withdrew it. I was about to contact the police because it looked like a criminal offence had been committed.

"I hope this sends out a message that forging nomination papers is defrauding the electorate and is a serious offence."

Oxfordshire Conservative Group agent Wayne Lawley said finding the culprit was "mission impossible".

Mr Lawley added: "We took this complaint seriously, but it's not the first time it has happened, and it happens to other parties too."