A three-day Tube strike will go ahead next week after talks failed yet again between union bosses and London Underground.
Members of the Rail and Martime Transport union (RMT) will go on strike for 72 hours from 9pm on May 5 as part of continued industrial action over plans to close ticket offices and cut 960 jobs.
It comes after a previous strikes last week which affected commuters on Tuesday and Wednesday morning last week.
Talks were held at the conciliation service Acas on Friday but broke down, prompting more angry words from both sides.
Mick Cash, acting general secretary for the RMT, said he was "angry and bitterly disappointed".
In a statement released late on Friday, Mr Cash said: "RMT negotiators worked flat out today at ACAS to try and reach an agreement which could allow for a suspension of the action and late this afternoon we had workable framework which could have triggered that suspension.
"However, right at the death LU changed tack and lobbed in a hand grenade, demanding not a suspension of the action but that the entire dispute be called off, pre-empting the outcome of the next stage of the process and imposing a condition that they knew we could never agree to.
"I am angry and bitterly disappointed that a deal which could have allowed for a suspension of tube strike action has been wrecked at the last minute and we suspect the intervention of the Mayor who seems hell bent on using this dispute to further his own political objective of leading the Tory Party.
"It is a cynical and politically motivated move that means that avoidable action now goes ahead as our members continue the fight for jobs, services and safety."
The Mayor of London, Boris Johnson, said he was "baffled" by the planned strike, saying three per cent of tube journeys involve a visit to ticket offices, which London Underground have said costs £50m a year to run.
Phil Hufton, London Underground's chief operating officer, said: "Despite our offer to continue talking, their interest seems to be in preserving the past and forcing London's fare and tax payers to foot the bill."
The RMT and London Underground have met more than 40 times through Acas, the conciliation service, since a two-day strike was held in February.