Millions of pounds spent by Oxfordshire's police force investigating the summer's airline terror bomb plot could have "severe implications" for its finances, a report has revealed.

Thames Valley Police Authority submitted a claim to the Home Secretary on Friday, asking for the cost of the past four months' counter-terrorism campaign, Operation Overt, to be fully reimbursed.

The police authority estimates the investigation, launched in response to allegations terrorists were trying to smuggle explosives into aeroplanes in hand luggage, cost it £7.89m. Many officers were diverted from regular duties to search woodland in Buckinghamshire and the operation will officially will end on Friday.

Acting Chief Constable Sara Thornton said: "The Police Authority has taken the view that there should be full reimbursement because it is not right for taxpayers of the Thames Valley to pay for a national and international operation of this size."

A briefing report issued by the authority calls on the Home Office to consider the impact on police finances if the Government cannot provide funding.

It reads: "There will be severe implications for both the draft revenue estimates for 2007/08 and the authority's general balances and reserves if these costs are not reimbursed."

Without Government help Thames Valley Police general balances will be reduced from £10.8m to just £2.9m. A decision is due in January.