Union leaders called today for urgent talks with London's mayor to avert two 48-hour strikes by London Underground maintenance workers.
Members of the Rail Maritime and Transport union employed by Tube Lines are due to walk out from 7pm on June 23 and again from 7pm on July 14.
The union said it had been unable to receive assurances on jobs, working conditions and pay as the company's work transfers to Transport for London (TfL).
The strike will have "severe consequences" across the Tube network, especially the Piccadilly, Northern and Jubilee lines, which are maintained by Tube Lines, said the RMT.
General secretary Bob Crow said today: "With TfL and the mayor making a big noise about buying out and taking over Tube Lines, they also need to take responsibility for the mess that the company have left behind and that includes the dispute over jobs, pay and working conditions with the Tube Lines employees.
"The mayor cannot wash his hands of this dispute, which will cause massive disruption for Londoners if we fail to get assurances on the key points that have provoked the strike action. He needs to show some real leadership and that means direct talks with RMT now that he is calling the shots at Tube Lines.
"If the cuts on Tube maintenance are allowed to let rip, there is no question that lethal corners will be trimmed, with disastrous consequences.
"We need direct talks right at the top to hammer these issues out. We are getting nowhere with the zombie management at the rotting corpse of Tube Lines."
A TfL spokesman said: "As the RMT leadership knows, we do not currently control Tube Lines. We are working to conclude the acquisition of the company by the end of June, which will benefit all Londoners by effectively ending the PPP (public private partnership), which has wasted hundreds of millions of pounds and led to delays to upgrade work.
"The RMT have time and again called for Tube Lines' work to come back under public control, and that is what we are working to achieve. Furthermore, this is an existing dispute about pay and conditions and not about the proposed transfer of Tube Lines to TfL.
"We strongly urge RMT leadership to call off the threatened strike action and to enter proper dialogue with us after our acquisition of Tube Lines."
A spokesman for the Mayor of London said: "The RMT are well aware that the Mayor has made it clear he will not meet with unions threatening strike action on the capital.
"Rather than threatening disruption the RMT should call off their strike action and hold talks with TfL once their purchase of Tube Lines has been completed."