Fresh talks will be held on Monday to break the deadlock over new all-night underground services in London that have triggered two strikes in recent weeks, causing widespread disruption.
The conciliation service Acas will chair the talks, with the unions likely to walk out again, possibly for 48 hours, unless there is a deal. Workers are unhappy with shift arrangements for the all-night tubes, due to start on 12 September.
Boris Johnson, the London mayor, has admitted the introduction of all-night services faces delay because of the dispute, but has ruled out direct talks with unions.
Johnson indicated the night tube start date could be postponed – a concession that may allow time for negotiations to avert further strikes. The mayor said he was “not fussed” about the new service starting on 12 September: “I want it starting in the autumn – what I am fussed about is the offer being put to union members.”
Unions called for direct meetings with Johnson after his comments. Transport for London (TfL) has confirmed the date was likely to slip, and that London Underground had always regarded it as a target that could only be reached with agreement, and not if the price was too high.
The dispute is over terms and conditions for the night tube, which will see 24-hour services on central London lines at weekends. Although London Underground said no staff would be forced to work longer hours or additional shifts, and that employees could choose to work nights or not after a transitional period of up to a year, unions are seeking guarantees that TfL appears unwilling to give.
Staff have been offered 2% and a guaranteed 1% or RPI-matched rise next year, as well as bonus payments for drivers working the night shifts, but union representatives insist that pay is not the sticking point. The RMT union said the introduction had been rushed and could jeopardise maintenance, threatening the quality and safety of the wider tube service.
Last Thursday’s industrial action brought by all four tube unions caused widespread disruption, as commuters sought to find alternative means of transport from the tube, on which normally 4m journeys are made daily. Unions said the industrial action by their members was “rock solid”. Last week’s strike was the second in a month, following one on 9 July.
