Tube unions have demanded direct talks with Mayor of London Boris Johnson in a bid to avoid two crippling 48 hour strikes.
London Underground maintenance workers for private, soon to be public firm, Tube Lines are walking out over a "lack of assurances" over the transfer.
Members of the Rail Maritime and Transport Union says it has been unable to receive assurances on jobs, working conditions and pay as the company's work transfers to Transport for London.
Johnson has been warned of "severe consequences" across the network - strikes from 7pm on June 23 and again from 7pm on July 14 will have a serious impact in the Piccadilly, Northern and Jubilee lines.
Not for the first time TfL are caught in the middle, with public transport held to ransom by disputes in the private industry - pay parity bus strikes the previous bogeyman.
A TfL spokesman argued that it does 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 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."
Industrial action followed a nine to one vote for strikes. The impact could spread beyond the Tube's three busiest lines as the Emergancy Response Unit, that deals with urgent repairs that keep the system running, is run by Tube Lines on behalf of the whole of London Underground.
Mayor & TfL "need to take responsibility"
RMT general secretary Bob Crow said after the big noise made about taking over Tube Lines, the Mayor and TfL "need to take responsibility for the mess that the company has left behind" including disputes.
"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."
Boris Johnson made a "no strike" deal a major part of his transport manifesto, a policy that has been met with little success.