Talks over an all night Tube in London have broken up without agreement and the new service will not come in this year, union sources told the Press Association.
In August London Underground announced the service would be postponed.
The all-night tube service, set to run on selected Friday and Saturday evenings, was due to start on 12 September.
No new commencement date was given.
In a statement on Wednesday, Finn Brennan from the train drivers' union, Aslef, 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 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.
"London Underground 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. Underground management have completely mishandled these negotiations. They have wasted every opportunity for a settlement and seem to have been determined to provoke confrontation rather than resolution."
In August LU's managing director Nick Brown said the organisation was close to reaching an agreement on pay and conditions.
He said: "Further to the progress made in recent days with the trade unions and the suspension of strike action, we believe we are not far from an agreement that protects the work-life balance of our employees and is affordable, sustainable and fair.
"As such, we have decided to defer the introduction of Night Tube to allow more time for those talks to conclude. Our objective is to reach an agreement that ends this dispute and delivers the Night Tube for Londoners this Autumn.”
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Workers had been set to stage two two-day strikes before the postponement, but they were called off at the last minute
as a “goodwill” gesture, according to Unite.
In July, unions staged their biggest walkout in 13 years over the introduction of the night tube.
The Rail, Maritime and Transport union (RMT) described the service as a "vanity project" of Mayor Boris Johnson, claiming it was "fundamentally flawed from top to bottom".