Industrial action could take place before Christmas
Engineering and electrical workers on London's Underground network have voted for industrial action in a pay dispute.
The Unite union, which represents the 500 workers, wants further discussions over a London Underground pay offer of 1.5% for 2009-10.
Union officials will decide on Tuesday what form of action will be taken, but strikes have been ruled out.
Transport for London said the pay deal offered stability and it called for meaningful discussions.
John Morgan-Evans, Unite regional officer, said Tube bosses were risking the possibility of more disruption.
He said: "This vote shows that our members' admirable patience has run out. They have decided they do not want to take strike action but want to make their point with other forms of action."
The industrial action could be taken before Christmas, officials said.
Steve Hart, the union's regional secretary, added: "London's public transport is facing a serious threat as industrial relations deteriorate on buses and now the Underground."
Meanwhile, the Rail Maritime and Transport Union is planning to ballot members over the same pay dispute.
Richard Parry, managing director of London Underground, described turnout for the ballot as low.
He said: "The Unite leadership has failed in its bid to get a mandate for strike action and I urge them to return to meaningful discussion now.
"There is absolutely nothing to be gained from taking more strike action in the current tough economic climate at a time when many Londoners have seen their pay frozen or have lost their jobs this year."