The Night Tube service, originally due to launch in September this year, is unlikely to start until next year, according to union bosses.
Talks between London Underground and unions, following numerous strikes this year, have reportedly broken down without an agreement.
Finn Brennan, ASLEF’s organiser on London Underground (LU), said: “We have made it clear to London Underground that we want to keep talking and develop a solution that delivers Night Tube while protecting and improving the work-life balance for our members.
“We have put forward a number of proposals to resolve this dispute in a way that is fair and benefits both sides. LU have rejected them all.
“Most disappointingly of all, they have decided to blackmail their own employees by refusing to make a pay offer unless staff agree to worsen their working conditions.
“That is not something we are prepared to accept. The management of London Underground has completely mishandled these negotiations.
“They have wasted every opportunity for a settlement and seem to have been determined to provoke confrontation rather than resolution.”
Before the September postponement , the Mayor of London had backed away from a firm date but insisted that the launch would come in the autumn.
However, RMT union boss Mick Cash claims: "Boris Johnson has rung his officials from Japan and instructed them to kick the Night Tube into next year."
The Night Tube has recently come under fire after it was revealed that it may only benefit London's high earners , according to one report, and one Kensington resident claiming the noise will make her life a "complete misery".
Future strikes?
RMT general secretary Mick Cash said: "This crisis management of the Night Tube could have been avoided if LU hadn't chosen to try and railroad through imposed rosters and had stuck to the agreed negotiating framework from the off.
"No one wins from this situation - neither Londoners or tube staff. RMT supports the principle of a Night Tube with properly agreed reward and rosters and the union remains available for further constructive talks.
"RMT is frankly astounded that Boris Johnson has rung his officials from Japan and instructed them to kick the night tube into next year. RMT is seeking further urgent talks at the most senior level to get this process back on track."
LU's chief operating officer Steve Griffiths said: "We've made significant progress over the last few months.
"Our offer has been reworked considerably from where we were when the trade unions balloted their members for strike action, which is why we now feel we must seek the views of our staff, as the unions haven’t.
"Not only are the unions at risk of depriving millions of customers of their Night Tube service, they are depriving employees of a very fair pay offer and longer term opportunities to improve work life balance even further."
RMT union members are currently balloting for possible future strike action on the Piccadilly Line, with balloting set to close on October 20.
