More than 6,000 Metropolitan Police staff have voted to strike in a dispute over pay.
Members of the Public and Commercial Services (PCS) union are involved in a row over payment of a London allowance.
They will walk out after the were refused £1,250 in the allowance.
PCS general secretary Fran Heathcote said: "Our members in the Met Police have had enough of being treated like an afterthought.
"Their almost 100% vote for strike action sends a strong message.
"Police staff will not tolerate being treated as second-class citizens within their own workplaces and they will take action until they receive the same £1,250 allowance as their colleagues."
The move comes after around 300 Met staff walked out in a dispute over hybrid working in February.
Met Police officers are banned from taking strike action under the Police Act 1996, but this does not apply to the force’s civilian staff.