The cost to the public purse of giving London’s police officers a free ride on the railways has risen to £24 million a year, The Times has learnt.

The Metropolitan Police is facing Whitehall pressure over the cost of the perk, which enables its 31,000 officers to travel up to 50 miles (80km) beyond London without having to buy a ticket, even if they are off duty. Officers just show their warrant cards to inspectors.

With police forces around the country being told to make efficiency savings, the future of ticketless rail travel for the Met is under review.

Scotland Yard confirmed that its contract for the scheme with the Association of Train Operating Companies cost £16 million for 2008-09. Five years ago the scheme cost half that. The Metropolitan Police Authority (MPA) also has to meet an estimated £8 million tax liability because the travel deal is regarded by the taxman as a perk.

Free travel for officers was introduced on the Tube and buses in London in 1970 in response to a rise in crime and attacks on transport staff. A deal to extend that to overground trains was negotiated in 2001. The Met viewed it as a tool in recruiting and retaining officers who lived outside London. The Met said that the arrangement helped to cut crime on the railways, with each officer intervening to stop or prevent trouble three times per year on average.

The cost of the perk is negotiated every year in closed sessions at police authority meetings because they are regarded as commercially sensitive.

Peter Smyth, chairman of the Metropolitan Police Federation, said he was surprised that the cost of the rail perk had risen so high. “The recent recruitment drive to get the Met’s numbers up from 26,000 to 31,000 has been built on free travel,” Mr Smyth said. “To contemplate taking that benefit away would almost certainly result in many officers reviewing their position about where they want to work. It would have a big impact on the Met’s ability to recruit.” Mr Smyth said that rail companies would also lose the crime-reduction benefit of having officers on trains, as many would probably choose to drive to work.

A spokesman for the MPA said: “The agreed one-year extension for 2008-09 with the Association of Train Operating Companies was £16 million. The MPA also meets the cost of the tax liability, which is estimated at £8 million. The MPA is reviewing the costs of this scheme along with the rest of the £3.5 billion expenditure to provide a value-for-money budget to Londoners.”

The concession entitles police officers to free travel on London Underground, buses, trams and the Docklands Light Railway services, as well as certain routes on the overground national rail system, on and off duty. Special constables can travel free on the Underground, bus, tram, overground and DLR services, on and off duty. Police community support officers and traffic wardens are entitled to free bus travel while on duty.

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