Wiltshire's air ambulance will be scrapped and replaced with just one aircraft serving the county, Avon and Somerset and Gloucester under new proposals for a National Police Air Service.

Under the austerity plans, the number of police helicopters and air bases will be slashed by a third across England and Wales.

But, it is claimed the measures will provide a more effective and "joined-up" air service, while simultaneously driving down costs.

It is understood Wiltshire Chief Constable Brian Moore has spoken out against the proposal because of the county's unique joint deal with the NHS to fund the air ambulance.

Wiltshire Police Authority is contractually tied with the Great Western Ambulance Service, until 2014, for the provision of a police helicopter/air ambulance. The current arrangements in Wiltshire will remain as they are at present.

Wiltshire Police Authority chairman Christopher Hoare, said: “Wiltshire Police, Great Western Ambulance Service and the Wiltshire Air Ambulance Charity are committed to retaining an air support capability for the police, and also the provision of an air ambulance for Wiltshire.”

The assistant chief constable for Wiltshire, Patrick Geenty said: “All public sector organisations are under pressure to find efficiency savings, and the police service, nationally, has been working for some time to establish the maximum benefit from air support units.

"Wiltshire police are currently conducting a feasibility study on a number of options, but no final decision has been made to date.”

Andrew Hollimngshead, GWAS associate director said: “We remain fully committed to supporting an air ambulance in Wiltshire and GWAS is working closely with the Wiltshire Air Ambulance appeal and Wiltshire Police to ensure that the people of Wiltshire continue to have a helicopter resource to save lives.”

There are 30 police air bases in England and Wales that serve 33 aircraft, costing forces £66 million a year.

Under the plans this will be cut to 20 bases serving 23 aircraft - shaving £15 million off the air support budget.

The plan for Wiltshire would see the combined service based at RAF Colerne.

Rather than each force having its own helicopter patrolling its region, the new national service will be responsible for the whole of England and Wales and be operated from one central command centre.

There will also be a clear "user requirement" laid out, meaning cost-intensive flights will be approved only if they are necessary.

The groundbreaking proposals were put forward today by the Association of Chief Police Officers (Acpo), which has been working with the National Policing Improvement Agency.

Acpo president Sir Hugh Orde said: "This project is all about enhancing the service we already have for less money."

The project is already said to have the support of the majority of chief constables across England and Wales and is hoped to be officially rolled out in April 2012.

However, it will be the separate police authorities, who currently own the air bases and aircraft, who decide whether the "borderless" air service goes ahead.

As well as the proposed 23 aircraft - of which the Metropolitan Police will have three - there will be three spare helicopters on standby.

The oldest helicopters of the current fleet will be sold off along with some bases, which have large overhead costs. Acpo believes some jobs will be lost as a result of the overhaul, but said a number of officers would be redeployed.

Hampshire Police Chief Constable Alex Marshall has spearheaded the proposals and will be the head of NPAS.

He said that police helicopters across England and Wales currently offer 19 hours of coverage, but the new set-up would allow 24 hours.

The current response rate - which sees 97 per cent of the population receive air support in 20 minutes - would not be affected.

"There will also be a more specific user requirement focusing on searching for high-risk people who have gone missing, catching criminals who have committed a crime and for surveillance," added Mr Marshall.

"This is not merely a cost saving exercise. While the current service is capable of doing its day job, artificial boundaries have meant that helicopters are restricted to operating within their own force area. A national, borderless service will ensure effective coverage of urban and rural areas."

He added that if the proposals were given the green light and were successful, other aspects of the police service could be nationalised.

Sir Hugh, who represents the 42 police forces in the United Kingdom, said: "What we will get is a slightly enhanced service for less money without taking away from front line policing."

Not all forces have shown support for the National Police Air Service proposals.

South Yorkshire Police, which would have its helicopter withdrawn from service under the plans, claimed that the densely populated city of Sheffield would suffer.

The force's Chief Constable Meredydd Hughes said today: "The plan as presented today does not provide an adequate service to one of Britain's biggest cities, and treats Sheffield very poorly by comparison with Leeds, Bradford, Hull or Manchester.

"The proposal would rely on one of the UK police's busiest helicopters serving Leeds and Bradford to the north, and another currently serving Nottingham and Derby to the south, and there is no doubt that the response to Sheffield would be too slow, and far below the standard of today. The third helicopter proposed is based in Humberside."

Under the plans, aircraft serving the Merseyside, Cambridge and Dyfed-Powys regions would also be scrapped.

Sussex and Surrey would reduce to one aircraft, combine and relocate to a new base at Dunsfold.

Norfolk and Suffolk would also follow suit, relocating to a new base at RAF Honington.

Essex and Dorset's force aircraft would move their bases to Southend and Bournemouth Airport respectively, with aircraft serving West Midlands Police relocating to Wolverhampton Airport to form a two-unit base with West Mercia and Staffordshire.

Chief Constable Hughes added: "The report hides the deficiencies of the proposed service within generalised response times to the force as a whole, but it is the areas of highest crime; densest population; and major sports stadia which receive the poorest service."

The plans would also see aircraft covering Thames Valley, Bedfordshire and Hertfordshire withdrawn from service, with provision continuing from other bases in the area.