Cleaners and caterers at the Department for Business, Energy and Industrial Strategy (Beis) in central London are set to begin an indefinite strike this month.
The members of the PCS union are demanding that their employers—outsourcers Aramark and ISS—pay them the London Living Wage of £10.55 an hour.
Now they are preparing to escalate their battle, beginning their strike on Monday 15 July.
They will be joined by porters, security and post room workers who are also set to strike for five days from Monday 22 July.
The strikers will need solidarity from across the trade union movement, including fundraising and delegations to the picket lines.
The threat of a strike at London’s Tate Galleries has led to an improved pay deal from bosses.
It came after 95 percent of PCS and Prospect union members voted for strikes.
The employer “found some additional funds” after the vote.