Cleaners at the Houses of Parliament have voted to strike in a row about pay and holidays.
Cleaners will strike next week
Up to 170 members of the Transport and General Workers' Union (TGWU) will walk out for 24 hours next Wednesday.
The cleaners want a pay rise of £1.70 an hour from £5, as well as sick pay, better holidays and a company pension.
Jack Dromey, deputy general secretary of the TGWU, warned further strikes were planned, as well as other forms of industrial action.
He said: "The Parliamentary authorities have had every opportunity to act to end this scandal. The cleaners will wait no longer for justice."
A spokesman for the House of Commons authorities said: "This dispute is between the contractors and their staff.
"We have been working to see whether we can get some way towards achieving a mutually acceptable solution."
The strike will hit the House of Commons and the House of Lords a day before Parliament ends for the summer recess.
MPs and members of the Lords will have to walk past cleaners on picket lines.