London Underground workers could escalate industrial action unless a dispute over jobs and ticket office closures is resolved, a union is warning.

Members of the Transport Salaried Staffs Association are banning overtime in protest at staff being moved from ticket offices onto station concourses.

The union says there has been an increase in verbal and physical abuse from passengers since a programme of ticket office closures started.

The Rail, Maritime and Transport union is also involved in the row.

Lengthy talks between the two sides are due to end today ahead of a Transport for London board meeting tomorrow.

The TSSA is pressing for ticket offices to be reopened and job cuts reversed.

General secretary Manuel Cortes said: "Tube staff think there has been too much talking about the impact of ticket office closures and too little action to remedy the violence and abuse our members face.

"The TfL board have a chance to show Londoners that they will stick up for the Tube, for its workers, for its passengers and their safety.

"If they think they can get away with dangerously inadequate staffing levels, I warn them to think again.

"Right now, we are only implementing an overtime ban but we have a mandate for strikes and we will not hesitate to use this to secure the safe, fully-staffed Tube Londoners deserve."

London mayor Sadiq Khan ordered London TravelWatch to review the impact of the closures and job losses and while it recommended a number of moves to improve services, it did not call for the reopening of ticket offices.

Overtime has also been banned by station staff belonging to the RMT union in protest over the job cuts.

Steve Griffiths, London Underground's chief operating officer, said: "We have already been in discussions with TSSA at Acas and have started a joint review of staffing numbers and deployment with the trade unions. The independent review of the closure of ticket offices has been published by London TravelWatch and will feed into our joint review to ensure that we continue to deliver high quality customer service."