Tube maintenance workers are to be balloted over potentially more strike action over the Night Tube and pay, after union representatives rejected the offer on the table.
RMT said its reps had "overwhelmingly" dismissed the new deal, saying it mirrored proposals that had already been thrown out by workers on the rest of the Tube network.
The union will be balloting 1,300 members employed by Tube Lines, a wholly owned subsidiary of London Underground, who are responsible for upkeep on the Piccadilly, Northern and Jubilee Lines.
RMT general secretary Mick Cash said: “Our Tube Lines members have been offered the same deal on pay and Night Tube as their London Underground colleagues and our reps have clearly rejected it as wholly unsatisfactory and now we move to a ballot of our members for both strike action and action short of a strike. Preparations for that ballot are now underway.
“RMT has made it clear that with growing numbers of tube users, and planned expansions of the service, the staff in all grades who are expected to keep the railway running must be respected and their efforts properly rewarded. The union remains available for talks.”
Fellow union Aslef is also ramping up the fighting talk.
Finn Brennan, Aslef’s organiser for the Tube drivers, said: ‘London Underground last met with us in mid-November. We have repeatedly offered to have a concentrated period of discussions to resolve this dispute but they have refused to do this. Instead they have started a recruitment campaign for part-time staff without agreement on the terms and conditions under which they would work.
"Our members have now waited more than nine months for their pay rise and more than three years for promised talks on improving their work-life balance. Their patience is rapidly being exhausted.
"I will be reporting to our executive committee next week. If London Underground wants to avoid more industrial action, I urge them to sit down with us now for face-to-face talks to resolve this dispute. If they are not prepared to do so, then more strike action seems the only option left to us."