The capital’s long-awaited Night Tube looks set to shoulder further delays as fresh strike threats loom amid an ongoing row over pay and working conditions.

Around 1,300 maintenance workers are set to be balloted on industrial action, the Rail, Maritime and Transport (RMT) union announced earlier this week.

If it went ahead, the walkout would be the third backed by the union in less than six months. There is still no sign of when the weekend night service will commence, after the initial September 2015 start date fell through.

RMT general secretary Mick Cash said the same “wholly unsatisfactory” pay offer – a two per cent pay rise wihthin a four-year pay package – made to LU workers was also offered to Tube Lines. The body is a subsidiary of LU whose staff work on the upgrade and maintenance of the Piccadilly, Northern and Jubilee Lines.

“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,” he said, adding that preparations for the ballot were 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.”

The announcement came as Mayor of London Boris Johnson appeared announced TfL’s “no brainer” solution of hiring 180 new part-time Night Tube drivers. He told radio station LBC last Tuesday: “We’re doing a new approach. I can’t see any way it would fall foul with our friends at the trades unions.”

A spokeswoman for TfL said they were recruiting part-time drivers “to protect the work life balance of our staff” and to “deliver the Night Tube for London as quickly as possible.”

She added: “We are also recruiting part-time drivers specifically to run the Night Tube, therefore guaranteeing that no current driver will have to work the Night Tube unless they choose to do so.”