The Public and Commercial Services union (PCS) said up to 9,000 of its members in London would take part in the action on March 12 in protest at a below inflation wage offer.

Over 200 police stations in the capital will be affected by the strike, said the union, which complained that a 2.5% offer amounted to a pay cut because it was below the rate of inflation.

PCS general secretary Mark Serwotka said: "Below inflation pay is a growing problem across the public sector with the Government using the discredited argument that public sector pay fuels inflation to squeeze people's pay.

"Staff who play a vital role in the fight against crime aren't prepared to see their pay cut in real terms as the cost of living in the capital increases at nearly double of what is on offer.

"Met Police management need to recognise the important role that staff play by paying a fair wage."