Tube workers have called a 72-hour strike over inclusion in Transport for London's (TfL's) pension fund and travel benefits scheme.
Members of the Rail Maritime and Transport union yesterday voted 4:1 for strike action, and the union executive has called a strike beginning at 4pm on 24 April.
Staff at Tube Lines, one of the failed private organisations charged with maintaining the Underground network, have been demanding equal treatment with their Metronet colleagues.
Both companies are now wholly owned subsidiaries of TfL, but Tube Lines employees have not been allowed re-entry into the TfL pensions scheme or staff travel concessions.
This includes free travel within London and 75% of the cost of mainline rail journeys, matching all other tube staff.
RMT general secretary Bob Crow claimed TfL's current position was unjust and unfair while calling its negotiating "pig-headed".
"This is a massive mandate for action following a straightforward demand for parity with other Tube staff," he said.
"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.
"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 the depth of anger there is over this blatant lack of fairness and justice," he added.
Tube Lines staff are responsible for maintenance and upgrade work on the Jubilee line, Northern line and Piccadilly line.
They also provide a number of services including the Emergency Response Unit (ERU), Distribution Services and Trans Plant.
Neil Brown appointed interim head of UK wholesale distribution
Whose rules OK?
Latest news and analysis
To focus on STAR