Talks aimed at averting a 24-hour strike by London Underground workers from Sunday evening have collapsed and the walkout will go ahead, causing travel chaos in the capital.
Members of the Transport Salaried Staffs Association (TSSA) and the Rail, Maritime and Transport (RMT) union will strike from 6pm on Sunday in a long-running dispute over job losses and ticket office closures.
The unions met LU bosses for several sessions this week under the chairmanship of the conciliation service Acas but said no progress had been made.
RMT general secretary Mick Cash said: "Despite huge efforts by the union negotiating team, London Underground have failed to come up with any serious plans to tackle the staffing and safety crisis caused by the axing of nearly 900 safety-critical station jobs.
"Instead of resolving the issues, Tube bosses have chosen instead to ramp up the rhetoric with threats to mobilise a strike-breaking army of 'ambassadors' with severe consequences for the current safety regime across the Tube network.
"As a result of the management failure to face up to the current crisis, the talks have collapsed and all industrial actions remains on.
"It is up to London Underground to take full responsibility for this situation and to come back to us with a serious set of proposals."
Transport for London warned there will be a "severely reduced" service across the network on Sunday evening and all day on Monday.
Passengers were advised to complete their journeys by 6pm on Sunday, and that most Zone 1 stations are likely to be closed throughout the action.
There will be no services on the Victoria or Waterloo & City lines, or from busy stations such as Waterloo, King's Cross, Euston, London Bridge, Paddington or Victoria.
TfL has said it was committed to addressing recommendations in a recent report by London Travelwatch into the closure of ticket offices and has started working with the unions to review the staffing model and put more station staff roles back where needed.