Members of the Rail, Maritime and Transport (RMT) union across two of London's busiest stations have voted to strike over a staff member's dismissal.
The RMT said station staff across its London Bridge and Waterloo groups have voted in favour of walkouts and action short of a strike in a ballot, after one member was sacked and two other disciplined for their handling of an alleged fare-dodger.
The union said its executive was now considering the decision.
RMT general secretary Mick Cash said: "Our members have voted for action in support of their victimised colleagues at London Bridge and that ballot result will now be considered by the union’s national executive.
“This is one of the most appalling abuses of the LU disciplinary procedure that RMT has ever come across. This was a shocking, violent incident and those that bore the brunt of it should have been supported and commended by the company. Instead they have been sacked or disciplined in what is the most appalling multiple miscarriage of justice."
The union said one worker was sacked and two others disciplined for tackling a fare dodger said to have attacked station staff.
However, Transport for London (TfL) says the CCTV coverage it reviewed of the incident did not match the account given by the individual.
The union has called on TfL to reinstate the dismissed member of staff.
“London Underground should do the decent thing – reinstate our member, lift the disciplinary action and send out the message that fare-dodging and violence will not be tolerated and that staff in the front line will get the support and assistance that they need," Cash said.
TfL has been approached for comment.