by political editor Paul Francis

Police operations such as Operation Stack could be compromised under Home Office plans for forces to cut overtime.

The Kent Police Federation said it was concerned that the plans, part of a drive to save £500million over three years, could undermine operations.

Home Secretary Alan Johnson has announced plans for a major efficiency drive in the police, with proposals that would see spending across all forces slashed by £500million.

As well as greater collaboration between forces on the costs of cars and uniforms, there may also be cuts in police over time. An estimated £480 million is spent annually on overtime by the 43 police forces in England and Wales.

Ian Pointon, chairman of the Kent Police Federation, said there were widespread misunderstandings about police overtime.

He said the public wrongly assumed police officers could take overtime whenever they wanted when in fact it was an important part of major operations.

"It might be easy to stop overtime but if you do, there are implications for significant operations conducted by all police forces," he added. "Officers cannot simply stop in the middle of an operation and ride off. Take Operation Stack. Does Kent Police get extra money for this? No, it does not so you have to pay for it out of overtime."

Kent Police recently revealed it had spent more than £625,000 on overtime for Operation Stack in 2008. It also spent £628,000 on overtime costs for the policing of the eco-camp at Kingsnorth Power station.

Mr Pointon said there were opportunities to save money by cutting red tape.

"There is a difference between someone who is analysing patterns of crime and are providing targeted information for police officers and those producing lots of lovely graphs."

In a statement responding to the Government’s White Paper, Kent Police and the Kent Police Authority said they were already working closely with Essex to save cash.

"This joint work has identified significant savings that will help us achieve these [Home Office] targets. We are constantly looking at ways of saving money that can be used to enhance the work of police officers on the front line and this is part of that process. Each proposal is assessed against stringent criteria based around capability and efficiency."