Staffing a major anti-terrorism operation has cost Thames Valley Police £5.2m - and this could rise to £7m.

Officers from Thames Valley Police, including many from Oxford, have been helping the Metropolitan Police with Operation Overt - a search of woodland near High Wycombe, in Buckingham- shire.

Police authority member Lord Bill Bradshaw warned yesterday that if the Home Office refuses to foot the bill, the deficit could reduce local policing resources in Oxfordshire.

At yesterday's Thames Valley Police Authority meeting in Kidlington, he told the Oxford Mail: "If the money isn't forthcoming, the likelihood is that the number of uniformed police officers available to tackle the less urgent tasks would be reduced.

"They are bound to come from the basic command units in Oxfordshire, Berkshire and Buckingham- shire.

"Officers are doing overtime and we haven't got the money to pay them. If the work continues for another four to six weeks, the total bill could be £7m."

Fellow Oxfordshire member Carol Viney added that she was "staggered" that funding was in doubt and said she would be lobbying Henley MP Boris Johnson over the issue.

To add to the financial concerns, Thames Valley Police have been warned that the Home Office has only pledged to pay the additional costs of policing demonstrations against Oxford University's new animal testing laboratory until December next year.

The authority's treasurer, Bob Atkins, said a decision over funding for Operation Overt was being sought from the Home Office at the earliest possible opportunity and added: "At best, we may have a scaled-back offer of assistance - at worst, it may be none."

Acting Chief Constable Sara Thornton said she would draft a letter to all local members of Parliament raising the finance issue and added: "Quite frankly, standing in the woods in November and December is about the worst thing I can ask them (officers) to do."

The £5.2m deficit is not being factored into the authority's budget proposals, which were also outlined yesterday. The budget will be finalised in February, before council tax bills are issued.

In a report to the committee, Ms Thornton outlined £6.74m budget cuts for 2007-8, which would include civilianising 36 police posts, and cutting 74 support staff and 12 police officers' jobs.

These would not be frontline officers, and it is not yet clear which police roles would be most heavily affected.

If authority members set a budget that includes a council tax precept increase of less than five per cent, further staff could be lost.

If the tax increase for the police authority element of the bills is limited to three per cent, 75 frontline officers would have to go.

Hunt for evidence in the woods

Operation Overt was launched in August by the Metropolitan Police amid allegations of a plot to plant bombs on Transatlantic airliners.

The operation has included a search of houses in High Wycombe and of the nearby King's Wood, alongside the M40.

Anti-terrorist detectives arrested 23 people in the raids, and Thames Valley Police officers were deployed to help scour the woodland for evidence.

The BBC reported that police had found a rifle and a handgun during searches at two addresses, while sources suggested that "suspicious" components had been recovered - but this was not confirmed by Scotland Yard.

The alert led to increased security measures at British and US airports.

In 1999, Thames Valley Police submitted an £11m bill to the Home Office for major operations, which included the £4.8m cost of dealing with animal rights protests at Hillgrove cat farm, in Minster Lovell, and the multi-million pound cost of policing the Newbury bypass protests.