Union officials have said a Christmas strike on the London Underground could not be ruled out, as workers are due to be balloted in a dispute over job cuts and pensions.
About 1,800 Rail, Maritime and Transport (RMT) union members working for Tube maintenance firm Metronet will be asked to strike.
An RMT spokesman said, given the timescale of proceedings, a walkout at Christmas “could not be ruled out”.
Metronet said action was unwarranted and would cause huge disruption in the run-up to Christmas if it went ahead.
Tube drivers may also be asked to take action, the RMT said, because if Metronet workers walked out, the tracks may not be properly inspected.
As a result, 1,500 drivers will be asked to vote for action “short of a strike”, ie, work-to-rule, ovetime bans, and so on.