Workers who maintain and upgrade Tube lines on London Underground are to strike for 72 hours next week in a dispute 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 will walk out at 4pm on Tuesday until the same time on Friday.
The staff work on the Piccadilly, Northern and Jubilee lines and provide a number of services, including emergency repairs, across the entire network.
The row is over union demands for all Tube Lines staff to be allowed to join the Transport for London pension scheme and receive the same travel concessions as those who work for London Underground.
RMT officials said the strike will have a "widespread" impact on Tube services across the network.
The announcement follows a 4-1 vote in favour of industrial action in a ballot of union members.
RMT general secretary Bob Crow said: "RMT members have delivered 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, and our members have no choice but to strike to secure those basic rights.
"We have gone through all the negotiating channels 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 has resulted in this strike action being called.
"Former Metronet employees have been allowed back into the Transport for London (TfL) pension fund and now also have the same travel facilities as other LU employees.
"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 the strong mandate for this industrial action shows Tube Lines and TfL the depth of anger there is over this blatant lack of fairness and justice."
The planned strike comes just weeks before the London Mayoral election.
Tube Lines operations director Lee Jones said: "A strike on this issue is completely unnecessary and will not achieve anything.
"We urge the RMT leadership to end their strike threat and return to talks, as it will only be resolved through constructive discussion.
"The RMT's ballot showed that less than 44% of its members voted in favour of strike action. Any action would be by maintenance staff, not Tube drivers and station staff.
"Should a strike go ahead, we have plans in place which will enable London Underground to operate Tube services on all three lines and to minimise any disruption."
A spokesman for London Mayor Boris Johnson said: "It will come as no surprise to Londoners that, a week before the mayoral election, Ken Livingstone's RMT friend Bob Crow is trying to hit hard-working Londoners and businesses."
Mr Livingstone's deputy mayoral running mate, Val Shawcross, said: "The failure of Boris Johnson and the RMT to resolve their differences comes at a huge cost to Londoners. Now millions of Tube users are facing the huge inconvenience and disruption that comes with a Tube strike.
"It has been 1,444 days since Boris Johnson was elected and he has still not bothered to meet representatives of the Tube unions to discuss his manifesto promise to implement a no-strike deal.
"Boris Johnson's failure to get a grip of the Tube has led to more Tube strikes in the last four years than in the previous eight years."