Workers on some of the busiest rail services in the country are to strike on the Saturday before Christmas in the long-running dispute over guards on trains.

Members of the Rail, Maritime and Transport union (RMT) on South Western Railway (SWR) will walk out on December 22, causing travel misery for festive shoppers.

The company, which has been hit by a series of delays in recent weeks because of signal and train failures, runs services into London Waterloo, the busiest station in the UK.

RMT general secretary Mick Cash said: “South Western Railway continues to refuse to resolving this dispute, which is about safety, security and access while the company look to open up a loophole that would allow them to run driver-only services at their discretion.

“Recent figures have shown a shocking a surge in violence on our railways. It is frankly appalling that South Western Railway are looking for a green light to throw the guard off their trains as and when they see fit in the name of profit.

“SWR might think it’s acceptable to play fast and loose with passenger safety, security and access but RMT members, who have stood firm throughout this dispute despite appalling harassment from the company, will not accept a dilution of the safety regime on the railway.

“There’s a simple solution to ‎this dispute and it means SWR stop playing with words and negotiate the guard guarantee that reflects the safety values of the agreements RMT has pinned down in other parts of the rail industry.”

RMT members on Arriva Rail North are striking for 24 hours on every Saturday for the rest of the year in the same dispute.

ARN (Northern) said few services will run after 5pm on Saturday and warned that its trains will be “extremely busy”.

Managing director David Brown said: “By the end of December, we will have had 19 consecutive Saturdays of RMT strike action.

“This targeted action disrupts our customers’ lives, but, as we enter a vital period for businesses, it also damages the economic wellbeing of the north of England.

“We have fantastic colleagues who have supported customers by keeping our trains running on each of the RMT strike days.

“We are aiming to keep as many people moving as possible and ensuring customers can still travel into the biggest towns and cities for the big seasonal events including Christmas markets.”

Richard Allan, deputy managing director of Northern, said: “We can assure all our customers that there will be a suitably trained and qualified Northern employee on the train, in addition to the driver, who will be able to help any customer who needs support with access, personal security, information, ticketing and so on.

“We have promised our conductors that their future role will be on-board our trains, we can guarantee that role until at least 2025, their current pay will be protected and their pay will be reviewed annually, if RMT ends its damaging dispute.

“This assurance for customers and conductors alike means there is no reason for RMT to continue these strikes, which are causing problems for customers, businesses and the wider economy.”

A South Western Railway spokesman said: “By targeting the last Saturday before Christmas when people are trying to travel to be with family and friends the RMT is ensuring the maximum misery is inflicted at what should be a time of relaxation and enjoyment.

“This action is totally unnecessary. We have guaranteed to roster a guard on every train, and we need more, not fewer guards – 70 more by May 2019 – and we have an opportunity with the introduction of the new suburban trains to operate these trains differently to maximise the customer benefits.

“The RMT is scaremongering by using crime in its statement. The number of crimes on the SWR network has reduced by nearly 6% since April. SWR’s team of 35 Rail Community Officers work on trains and at stations to prevent and detect crimes. They work closely with BTP officers to help reduce incidents on the network, engaging with customers and highlighting suspicious activity.

“Should this action go ahead, we will do everything we can to provide the best service possible for our customers.”