RMT announced on Wednesday that it would also be balloting its members who work for Tube Lines, a company that runs the Piccadilly, Northern and Jubilee lines.
General Secretary Mick Cash said: “Tube Lines staff have been offered a deal over the next two years on pay and 24-hour running which mirrors that on offer to the rest of the LU workforce.
“It is as unacceptable on Tube Lines as it is across the rest of the combine and as a result these essential maintenance staff will now be balloted for both strike action and action short of a strike.”
This is something that is of massive benefits to working people.Boris Johnson
On Tuesday the RMT called for the immediate and indefinite suspension of Mr Johnson’s “night tube vanity project”.
Mr Cash said: “Millions of week day commuters, who fork out a fortune in fares, risk seeing their safety compromised and their services reduced to chaos so that a few thousand revellers can be shipped home in the early hours of Saturday and Sunday morning and experienced tube managers know that.
“We urgently need to get talks convened with tube professionals who understand the reasons behind a crisis which should never have been allowed to get this far.”
But Mr Johnson said the night Tube is the “right way forward for London.”
“The idea of the night Tube is something that is not just for kind of party animals in London.
“This is something that is of massive benefits to working people. 50 per cent of the people who use our night buses at the moment are going to and from work.”