Union leaders stepped up their opposition to the London Under-ground Public Private Partnership (PPP) this week, threatening to call out workers at Tube Lines as well as Metronet.
As CJ went to press more than 2,000 Metronet maintenance workers were preparing to down tools for 72 hours. A further three-day stoppage is planned for next week.
The move follows a breakdown in negotiations after the Rail, Maritime & Transport union (RMT) failed to obtain "unequivocal" guarantees that there would be no job losses, forced employee transfers or pension cuts in the wake of Metronet's collapse into administration in July.
The RMT has turned its sights on Tube Lines, which maintains and upgrades the Jubilee, Northern and Piccadilly lines. A spokesman said: "The collapse of Metronet has also exposed the risk to workers on Tube Lines. The RMT is demanding assurances from Tube Lines on the future of its members' jobs and pensions." The RMT has given Tube Lines until Wednesday (today) to respond.
A Transport for London spokesman said: "Both the administrator and Metronet have made it clear there will be no threat to jobs, no transfers and pensions will be protected."