A protest will be held on Friday to mark three years since the start of the bitter dispute about guards on trains.

The Rail, Maritime and Transport (RMT) union will stage a demonstration against Southern Railway in central London.

The union has reached agreements with a number of other train operators about the role of guards, but the row with Southern remains unresolved.

The union said rail workers from across the country will join the protest, outside the offices of Keolis, which owns part of Southern franchisee Govia.

RMT general secretary Mick Cash said: "Since the dispute began on Southern, RMT members have been involved in similar campaigns against other companies over attempts to remove the guard from the train.

"Only on Southern have we been faced with such a stubborn and point-blank refusal to enter serious discussions.

"The union thanks the travelling public for their support and understanding throughout our campaign to put safety and access to services for everyone using our railways right at the top of the agenda."

A Southern spokesman said: "Since we made the change opposed by the RMT over two years ago, performance and passenger service on Southern have improved, and more trains now run with a second crew member on board.

"Industry safety bodies have confirmed that having the doors closed by the driver is at least as as safe as by a conductor. We urge the RMT to end their unnecessary dispute."

The RMT said new figures obtained from Parliamentary answers showed that at least 15,000 Southern services have run without a second person on board since the introduction of driver only operations in 2017.

The union said that with most Southern stations unstaffed, "mass discrimination" was taking place against older and disabled passengers who no longer have the guarantee of a second member of staff to help them, including being table to turn up and go and travel on the train of their choice.

Mick Cash said: "Three years on in the fight to keep the guard on Southern Rail trains the shocking reality of the scale of discrimination against disabled passengers is laid bare.

"Despite all the promises that there would continue to be a second person on trains, ministers have now admitted thousands of Southern services are running with a driver alone.

"The situation is likely to be even worse than they are prepared to admit and it's time for the truth to be told.

"Disabled and vulnerable passengers were once guaranteed a guard on their services to provide assistance and protection.

"That is now no longer the case, as we can see in this appalling increase in discrimination against disabled and vulnerable passengers."

A Southern spokesman responded: "Only a tiny fraction of services - most recently as little as 0.5% - have run without their intended second person on board and under the old arrangements those would have been cancelled, inconveniencing thousands.

"To help those in need of assistance we now have more staff on board our trains and complaints have fallen by a third since we changed the role."

Southern added that under the old arrangements, the 15,000 services referred to by the RMT would have been cancelled, inconveniencing nine million passengers.