The Government is having to bail out plans for a new police helicopter because the world financial crisis sent the cost soaring.

The Chiltern Air Support Consortium, which includes Thames Valley Police, had already ordered a Eurocopter EC135 P2 helicopter, to be based at RAF Benson.

But the global financial crisis sent the cost soaring due to instability on the stock market.

A police spokesman said when the helicopter was ordered 18 months ago it was expected to cost about £4.37m.

But minor specification changes and sterling's slide against the euro and the US dollar had increased the cost by about £250,000.

Police spokesman David Paull said the Government had agreed to fund the shortfall.

An annual report on the police helicopter, published this week, showed it attended 1,004 incidents in Oxfordshire between April 2007 and April 2008.

It led to 98 arrests, found 17 missing people and evacuated seven people to hospital.

All seven patients were airlifted by the police helicopter at night because the South Central Ambulance Service Air Ambulance can only fly in daylight.

The helicopter, also based at RAF Benson, is not fitted with night-time equipment such as searchlights and a navigation system.