Security staff in the Houses of Parliament will stage a second strike on Wednesday in a dispute over pay and conditions.
The Public and Commercial Services union (PCS) said more than 300 of its members will walk out for 24 hours from 7am following a strike last week.
The union members are also undertaking an overtime ban and a work-to-rule until Friday.
PCS general secretary Fran Heathcote said: “In a powerful display of solidarity, dozens of MPs joined our members last week at a huge picket line in the Palace of Westminster.
“These MPs see up close the amazing work these members do every day to ensure their safety and the safety of others in the UK’s national parliament building.
“Our members are determined to take this hard-hitting action until they achieve their demands.”
