A Tube union has announced the longest strike in the history of the London Underground as the bitter dispute over the Night Tube showed no sign of easing.
The RMT said its drivers would refuse to turn up for work on the Victoria and Central lines every weekend evening from the New Year through to the summer.
The six-month protest, which was announced on Thursday morning, is the longest period of action ever announced by the RMT.
The action would involve drivers belonging to the RMT refusing to clock on from 8.30pm on Friday until 8am on Saturday, and from 8.30pm on Saturday until 8am on Sunday.
The protest will restart on Friday January 7 and continue each weekend until June.
The RMT said its legal mandate to strike extended to other Tube lines and it may broaden the action if Underground bosses failed to respond to its demands.
The union has been in dispute with Transport for London for months over the rosters used to staff the Night Tube, and has already taken eight days of strike action to coincide with the partial reopening of the Night Tube last month.
The most recent walkout involved a 24-hour protest on five lines – the Victoria, Central, Northern, Piccadilly and Jubilee – that caused widespread disruption last Saturday.
Union chiefs say the current working arrangements wreck the work-life balance of drivers because staff whose normal job is on the “day Tube” have to work four Night Tube shifts a year.
TfL has been able to keep the Night Tube – which only operates at weekend – running, but with a far less regular service than hoped.
At times there has only been a train every 30 minutes, rather than one every 10 minutes, and extra station staff were deployed to ensure passenger safety after platforms became busy.
RMT general secretary Mick Lynch said: “If London Underground and the Mayor thought this fight for progressive and family friendly working practices was going away they need to think again.
“Our members have been re-balloted and have delivered a solid mandate for action and its the failure of LU and Sadiq Khan to address the grievances at the heart of the dispute that leaves us no option but to confirm the programme of action today.
“RMT has repeatedly put forward cost neutral proposals that would repair the damage unleashed by deleting 200 driver posts and which would dig LU out of this mess. They have ignored us and that approach will have severe consequences for Londoners in the New Year.
“We remain available for further talks.”
Muniya Barua, managing director of policy at business group London First, said: “Londoners depend on a regular and reliable Underground service and for many the Night Tube is a lifeline, not just a Tube line.
“This action is disproportionate and will have major consequences for the economic recovery. We’d urge the RMT and TfL to get back round the table quickly.”
Nick Dent, director of customer operations at London Underground, said: “We’re disappointed that the RMT is continuing to push for strike action that would cause unnecessary disruption at a time when our customers need us most.
“We urge the RMT to join us for talks so we can work together to resolve this dispute.”