Drivers on London Underground's Night Tube have overwhelmingly backed a strike on the network in a dispute over career progression, the RMT announced on Tuesday (14 March).

The confirmation comes after IBTimes UK reported that the operators would back the industrial action. The union said more than 96% of the those balloted supported a walkout on the 24-hour service.

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The dispute is over part-time Night Tube operators allegedly being stopped from moving into vacant full-time positions for a period of at least 18 months, while other staff, including part-time Night Tube station staff, are eligible to apply for the roles.

"It is outrageous that London Underground have decided to discriminate against their Night Tube drivers," said Mick Cash, the general secretary of the RMT.

"This is a senseless and damaging policy that picks out one group of staff for negative treatment and of course the drivers are angry, and that is why our members have voted overwhelmingly for action. That ballot result will now be considered by RMT's Executive."

"RMT would call on LU to see sense, stop these stupid attacks on career progression and fair reward for overtime working and confirm that this discrimination against the Night Tube drivers has been lifted."

Aslef, the RMT's sister union, is also balloting its Night Tube members for strike action. The ballot result is expected to be announced on Thursday 16 March. No date has yet been set for the RMT's strike action.

Peter McNaught, operations director for London Underground, said: "Night Tube services have been running since August last year in line with agreements reached with the unions.

"We've met with the RMT to discuss and resolve the new issues that they have. We have invited the RMT to more talks later this week and I encourage them to continue discussions with us rather than threaten industrial action."

How much is the Night Tube worth to London?

A report for the independent body London First estimated that the Night Tube will be directly responsible for more than 2,000 new jobs, including 500 extra on the service itself.

The study also suggested the service could boost London's economy by £77m annually, with London's overall night-time economy worth £30bn a year by 2030.

According to TfL, the 24-hour service will cut night-time journeys by an average of 20 minutes, but some will be reduced by more than an hour. The Night Tube accompanies TfL's system of night buses, of which usage has risen by 173% since 2000.