London Underground workers have voted to go on strike in a row over ticket office closures, jobs and safety.
Members of the Transport Salaried Staffs' Association (TSSA) backed walkouts by 67% and other forms of industrial action by 9-1.
The union has warned that staff have been on the receiving end of "unprecedented" levels of verbal and physical abuse from passengers since Tube ticket offices closed.
A TSSA survey assessing the impact of so-called Fit For The Future operational changes in September revealed high levels of anxiety, with four out of five staff having experienced a sharp increase in verbal and physical abuse from passengers.
TSSA general secretary Manuel Cortes said: "Our industrial action ballot is not a localised matter for Londoners, it should concern everyone in Britain who comes to London or has relatives in our capital city because this is not a dispute about wages, it's our members being prepared to take part in a strike to let the world know that the Tube they are using is not fit for safe purpose.
"Our customer service assistants are overwhelmingly trying to warn the public that the Tube they use is not safe. We no longer have enough staff.
"Our members will as a last resort go on strike to safeguard passengers. They are prepared to forego wages and risk media and management wrath to let the public know that our capital's Tube is no longer safe enough.
"This strike vote must not be dismissed as mindless militant action. Instead it's an act of desperation by mindful and public-spirited customer service assistants at their absolute best by putting passenger safety before anything else."