Almost 6,000 fewer officers will be on the policing frontline in three years' time as a result of the Government's budget cuts, figures have shown.

A fifth of front counters in police stations will also close, the report by Her Majesty's Inspectorate of Constabulary (HMIC) found.

There will be 5,800 fewer frontline officers, but the proportion of officers on the frontline will increase to between 81% and 95% as the number of non-frontline officers is almost halved, with 7,600 going by 2015, the report said.

Some 137 police access counters, such as in libraries and supermarkets, will also open to help offset the closure of 264 front desks. The figures do not include those for Britain's biggest force, the Metropolitan Police, or for Cheshire, as they have not yet produced their plans.

In the last year, the overall police workforce has been reduced by 17,600 officers and staff, more than half of the total reductions planned by March 2015, the inspectorate added.

The Met was named as one of three forces which may not be able to provide an efficient or effective service for the public in the future. "In our professional judgment (and having considered local context, including police cost to the taxpayer), there is a risk that three forces may not be able to provide a sufficiently efficient or effective service for the public in the future," the inspectorate's report said. These were Lincolnshire and Devon & Cornwall, as well as the Met, the HMIC said.

Police workforces will be cut by 32,400 officers and staff by March 2015, including the loss of at least 15,000 officers, the HMIC report said. Some 2,700 officers were lost from the front lines by March this year, and this will increase to 5,800 (6%) by March 2015. The total frontline workforce will also be cut by 8,100 officers and staff, or 6%, while those in non-frontline functions will see the loss of 20,300 officers and staff, a third of the total.

The 43 forces in England and Wales need to close a funding gap of £2.4 billion by 2015 and currently have plans to make cuts of £2.1 billion, the inspectors said. Some £233 million of the £302 million shortfall comes from the Met.

Policing minister Nick Herbert said: "This report makes it clear that the front line of policing is being protected overall and that the service to the public has largely been maintained. The proportion of officers on the front line is increasing, the number of neighbourhood officers has gone up, crime is down, victim satisfaction is improving and the response to emergency calls is being maintained. While there are particular challenges in three forces, we know that the vast majority are rising to the challenge of reducing budgets while protecting service to the public."

But Paul McKeever, chairman of the Police Federation, said the report revealed "the smokescreen that some forces are saying the frontline is not affected by moving officers from important functions elsewhere". He said: "Whichever way you cut it, the resilience of the police service to be able to react to whatever is thrown at it is being threatened. Forces will now look through the fine detail of the HMIC report, but the overall message is very clear. It's not too late to stop the rot; the Government must be brave, reassess the level of budget cut over the four-year period and do all it can to protect the public by preserving the best police service in the world. They will have the support of the Police Federation and every police officer to do this."