RECORD numbers of police officers are leaving Oxfordshire for better pay in London.

In the past year, 78 officers left Thames Valley Police to join the Metropolitan Police - the largest exodus for six years.

And the Oxfordshire branch of the Police Federation, which represents rank-and-file officers, fears even more experienced officers will be poached over the next four years, to cope with the demand of policing the 2012 London Olympics.

The federation and Thames Valley Police's Chief Constable Sara Thornton have been working together to try to get the Government to increase financial benefits for local officers, to stop experienced staff leaving.

Maurice Collins, chairman of the federation, said the Met had stepped up recruitment in the area because it was losing officers to forces in the North of England.

He said: "The demand for more officers at the Met has increased and is not going to go away.

"Not only are more and more officers needed in London in the fight against terrorism, there is demand for Terminal Five at Heathrow and, of course, the London Olympics.

"The Olympics are only four years away and Thames Valley is very vulnerable.

"It's now a critical issue. Go back five years ago and the average length of service here would have been around six or seven years - now that's about two-and-a-half to three years.

"I cannot knock the energy and commitment of officers, but in terms of experience, losing these officers doesn't benefit the community."

On average, officers earn about £5,000 more a year in London. But they can continue to live in Oxfordshire and take advantage of free subsidised transport offered by the Met for travel to work.

The Met also pay a "bounty" to officers for those who help recruit a policeman from another force.

Ms Thornton and the Police Federation spoke at a Home Office select committee meeting in Reading last month, raising the problem of officers being snapped up by London.

Ms Thornton has been campaigning for the Government to increase the annual allowance for Thames Valley officers - introduced five years ago to stop police leaving for jobs in London - by £1,000 a year.

Records show 78 police officers left Thames Valley for the Met between May last year and April this year, of which at least six were uniformed officers from Oxford.

During the same period in 2006-7 42 switched forces, while in 2005-6 18 officers did; in 2004-5 44 left and in 2003-4 58. In 2002-3 86 left for London.

Ms Thornton said: "We're concerned to have lost 78 experienced police officers to the Metropolitan Police over the past year.

"We're working with police forces around London and the Metropolitan force to limit the drain, in order to protect policing in the region. We're also seeking flexibility to give our officers more money in allowances."