The union said the walkouts by staff at Rail for London (Infrastructure) Limited were “highly likely to bring the Elizabeth line to a halt in the first strike of its kind since the line was opened in May 2022”.

The dispute centre around pay and proposed changes to pensions, with members voting nine to one in favour of strike action, which will take place on Thursday 12 January 2023.

Action short of a strike (effectively comprising a ‘work-to-rule’ instruction to only work contracted hours, take breaks and not provide contingency cover) will run from 12 January to 28 February 2023.

TSSA organiser, Mel Taylor said: “Frankly, we have been left with little option because we know workers at Rail for London Infrastructure (RfLI) are being paid significantly less than equivalent colleagues across the TfL network.

“That is simply not good enough. Our members have the power to bring the Elizabeth Line to a standstill and the company must now wake up to that fact and get back round the table.

“We are always open to talks, but only if there’s a much-improved deal in the offing, one which puts our members on a par with those in the outsourced parts of the Elizabeth line.”

The Elizabeth line opened in May 2022 and runs from from Reading and Heathrow in the west of London to Shenfield and Abbey Wood in the east.