London Underground staff could strike in protest against controversial plans to close Tube station ticket offices and axe hundreds of posts across the capital.
A raft of changes are planned by Transport for London as part of spending cuts of more than £40m a year, putting more than 750 jobs at risk.
The authority is trying to avoid compulsory redundancies but more than three quarters of RMT union members who voted voted were in favour of a strike and even more wanted other industrial action.
General secretary Bob Crow said: “The staff remaining are going to be forced through the humiliating and degrading experience of re-applying for their own jobs – the same staff who have been hailed as heroes when the tube has faced emergency situations.
“That is a kick in the teeth.”
He claimed the changes would make the Tube a "criminal's paradise" and affect vulnerable and elderly passengers.
Another rail union, the TSSA, will start its own ballot next week and executives will decide what action to take.
Manuel Cortes, general secretary, highlighted London Mayor Boris Johnson’s U-turn on his previous promise to protect ticket offices.
He said: “It was the Mayor who came into office in 2008 with a firm pledge to keep open every ticket office on the grounds of keeping passengers safe and secure at all times.”
Transport for London’s changes are some of the biggest ever attempted on the network.
More ticket machines will be put into entrance halls when 260 ticket offices are shut by 2015, and staff stationed elsewhere in stations.
New visitor information centres will be opened in major central London stations and some will see a boost in staff.
The Central, Piccadilly, Victoria and Jubilee lines and part of the Northern line will be open all night on Friday and Saturday from 2015.
But the plans prompted concerns from disability campaigners and passenger groups staff levels and assistance.
Access campaign group Transport for All protested after the changes were announced.
Member Jeff Harvey uses a powered wheelchair and ventilator on the Tube and often has to wait for help.
He said: “Often I cannot speak loudly and I cannot reach out to operate a ticket machine or swipe my card to open a gate.
“With a ticket office, there is always a person in a known location who I can communicate with.”
Phil Hufton, London Underground chief operating officer, said threatening industrial action was “totally unnecessary”.
He added: “In future, there will be more staff in ticket halls and on platforms to help customers buy the right ticket and keep them safe and secure.
“We’re committed to working with unions and staff to implement changes to station staffing without compulsory redundancies and we’ve been clear that there’ll be a job for everyone at LU who wants to work for us and be flexible.”
A London Underground spokesman said fewer people were buying tickets from offices in recent years and staff would be less “remote” from customers after the changes.
Only 30 per cent of RMT members balloted took part in the vote, he added.