Cleaners at the Houses of Parliament are set to hold a second strike for better pay.
Cleaners will be keeping their mops outside Parliament on 9 November
The Transport and General Workers Union (TGWU) said the cleaners had "no alternative but to mount picket lines".
It claims Parliamentary authorities have failed to attend meetings to resolve the long-running pay dispute.
Many MPs and peers support the 140 cleaners' campaign to increase their hourly rate from £5.20 to £6.70, after a 24-hour stoppage in the summer.
Union officials said the Serjeant at Arms - who heads the non-political staff in the Palace of Westminster - thought a meeting "would probably achieve nothing".
Deputy General Secretary of the TGWU Jack Dromey said: "It seems inconceivable that unelected, privileged civil servants are blocking attempts by parliamentarians to get their cleaners a living wage.
"MPs, Lords and the public recognise the justice of the cleaners' claim."
Politicians and peers will have to cross picket lines and clean their own offices on 9 November.