Ex-Conservative councillor Raja Akhtar is facing a spell behind bars after a jury found him guilty of hijacking a voter's poll card to secure his re-election in the city's Central ward.

But jurors were deadlocked on three further charges of forgery following a month-long trial, and prosecutors have decided not to take the matter any further.

A spokesman for the Crown Prosecution Service (CPS) said: "Following the conviction, we considered whether there was a public interest in a retrial for Akhtar.

"After careful consideration, it was decided that a retrial and conviction on the three remaining counts would not significantly add to the sentence he is likely to receive for this conviction. The further cost to the public of such trial was also considered."

Akhtar (48), who served as city mayor in 2004 having first been elected to the council in 1997, stood trial alongside fellow former Tory councillor Abdul Razaq at King's Lynn Crown Court last month.

The pair were accused of diverting postal votes belonging to members of the ward's largely Asian community to the addresses own friends and relatives before casting the ballots for themselves.

They were caught out in the course of a massive police investigation into voting irregularities sparked after residents in the area complained they had been unable to take part in the June 2004 election.

Operation Hooper, which was led by Detective Chief Inspector Ian Tandy, involved four years of work trawling through 11,000 documents, interviewing 1,200 witnesses and cost Cambridgeshire police about £1 million.

Both men denied the charges against them, but Razaq (52), of Alexandra Road, Millfield, was found guilty of six separate counts of forgery by the trial jury.

Akhtar, of Newark Avenue, Peterborough, was convicted of a single forgery charge by a majority verdict of 10 to two.

But even after five days of deliberation, jurors could not reach a decision on three other counts prompting the CPS to drop the charges.

When the pair are sentenced later this month, police are likely to apply for the charges to lie on file, meaning they could be investigated again if Akhtar were ever to be prosecuted on another matter.