Workers on London Underground are starting to vote on whether to strike in a dispute over the sacking of a colleague.

Members of the Rail, Maritime and Transport union who work at London Bridge and Waterloo - among the busiest stations on the Tube - will decide in the next few weeks if they want to launch a campaign of industrial action.

The union has warned it could escalate the dispute across the Tube.

The RMT says a worker was sacked and two others disciplined for tackling a fare dodger said to have attacked other station staff.

LU disputes the union claims.

RMT general secretary Mick Cash said: "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 is looking at a planned escalation if London Underground continues to pursue this outrageous vendetta against staff members for simply doing their job in a violent situation."

Phil O'Hare, general manager for LU's Jubilee line, said: "Our investigation into this incident included reviewing extensive CCTV footage.

"We are satisfied that his conduct on that day was not in line with the standards we expect from our staff.

"We take a zero tolerance approach to violence against our staff but similarly expect our employees to adhere to acceptable standards of conduct and behaviour when dealing with members of the public."