Police in West Yorkshire are sitting on a £26.7 million "rainy day fund" - enough to pay for 535 extra officers a year - according to Government figures.

Statistics released to Parliament by Police Minister Hazel Blears indicate that huge sums of money are gaining interest in West Yorkshire Police Authority's account.

But West Yorkshire Police has disputed the figures and claimed their reserves were within recommendations set down by the Audit Commission.

Guidelines say forces should keep an emergency reserve of two per cent of their annual budget, which was £407.6 million in the year to March, but the county's force is sitting on a reserve of 6.6 per cent, according to the Minister.

But West Yorkshire Police insisted the reserve fund figure for 2004-5 was around £7.1 million. The general reserve for 2005-6 is £8.7m - two per cent of the budget, which is the basic amount recommended by the Audit Commission, said a force spokesman.

The spokesman added there was also £5.5m earmarked as a capital reserve for building work. Today, the Conservatives said the money would be better spent recruiting more bobbies to patrol the streets.

A policeman costs £50,000 a year to put on the beat, a figure comprising the £31,450 average salary plus training, equipment, support and pension costs. Nationally, police have £950m sitting in the bank - enough to pay for 19,000 extra officers.

The figures revealed that the Metropolitan Police tops the "rainy day fund" list with £186m, or 6.7 per cent of its annual budget, in reserve.

A Home Office spokesman said: "There is not a set amount. It is an operational decision for individual forces. In the past, Her Majesty's Chief Inspect-orate of Constabulary and the Audit Commission suggested a minimum of two per cent."

The Association of Chief Police Officers said forces had to keep money in reserve in case of unexpected pressures, such as a big murder inquiry.

Forces also keep back money if they are expecting a large number of retirements or a major building work or investment programme.

Councillor Mark Burns-Williamson, the chairman of West Yorkshire Police Authority said the Government's figures were wrong and described the claims that police were sitting on £26.7 million as "unbelievable."

He said the force's reserves were wiped out by the costs of policing the Bradford riots in 2001 which left tax-payers with a £10.7 million bill. And he said the authority had spent the last four years building the cash reserves up to minimum levels.