THE delayed Night Tube project still hangs fire as fitters and engineers employed by the TfL maintenance subsidiary Tube Lines vote whether to strike over their prospective pay and conditions. The RMT has called for further talks.

The plan, approved by Boris Johnson, was for trains to run all night on much of the deep tube network on Fridays and Saturdays from last September, but services cannot now start until after another Mayor has taken control.

The RMT accepted an offer for train operators and station staff earlier this year, but at the time was critical of the Tube Lines deal. RMT general secretary Mick Cash said his members in Tube Lines were 'furious' at the 'inferior' offer they had received. He added: "Our reps for this group of over 1,000 safety-critical staff have unanimously thrown the whole package out."

The RMT said: "The dispute is over the companies refusal to discuss outstanding pensions issues until after the eventual launch of the Night Tube operation. There are also major unresolved issues over Night Tube staffing arrangements and a threat to undermine PRP [Performance Related Pay] agreements through Tube Lines refusing to base budgets on the negotiated levels."

One point of conflict is just how many nights a week would be involved in Night Tube. The initial plan was for just two days, but the RMT fears that the agreement, as worded, could mean services being extended to some other nights as well.

A ballot for strikes or action short of strikes is now underway. Mick Cash said: “It is absolutely essential now that there is the earliest possible resumption of serious and meaningful talks on these issues and the union is ready to engage in those talks."

London Underground chief operating officer Steve Griffiths said: "We have made the same fair and sustainable four-year pay offer for Tube Lines maintenance staff as has been made for staff employed by London Underground.

"This will see an average 2 per cent salary increase this year and inflation-protected rises in 2016 and 2017. Pension arrangements for Tube Lines maintenance staff have been the subject of separate ongoing discussions."