Staff who work and maintain and upgrade the London Underground (LU) have voted to strike after disputes over pensions and benefits.
The Rail, Maritime and Transport union (RMT), which represents around 1,000 staff on the Tube Lines contracts, said its members backed walkouts by four to one.
The row is over union demands to be allowed to join the Transport for London (TfL) pension scheme.
They also want to receive the same travel concessions as those who work for LU.
The staff involved work on the Piccadilly, Northern and Jubilee lines and provide a number of services, including emergency repairs, across the entire network.
The RMT general secretary, Bob Crow, said: "This is a massive mandate for action following a straightforward demand for parity with other tube staff.
"This dispute is about justice and about ensuring that all groups of staff under the umbrella of London Underground receive the same rights and benefits.
"We have gone through all the negotiating channels on both these issues but Tube Lines has refused to budge and have refused to engage in meaningful talks and that pig-headed approach has raised the temperature on the shop floor and is reflected in this result."
Crow added: "Tube Lines is now a wholly owned subsidiary of Transport for London and there is simply no excuse for refusing to give equal pension and pass rights.
"The union remains ready to talk, and this strong mandate for industrial action shows Tube Lines and TfL the depth of anger there is over this blatant lack of fairness and justice."