A fresh wave of industrial action will be launched by rail workers on Friday amid bitter disputes over the role of guards.

Members of the Rail, Maritime and Transport union (RMT) on South Western Railway (SWR) will refuse to work any rest days for the next four days.

The union said the action will have a “serious impact”, although the company said it planned to run all its services.

The union is embroiled in long-running disputes over staffing and the role of guards on trains with five separate operators which have led to a series of strikes and other forms of industrial action.

RMT general secretary Mick Cash said: “It is frankly disgraceful that South Western Railway continues to point-blank refuse to engage with the union in meaningful talks over their plans to run trains without a safety-critical guard on board across this franchise.

“Instead, they have resorted to the crudest possible attempts to threaten, bully and harass our members fighting to put public safety before private profit.

“RMT has repeatedly said that South Western Railway should call off these disgraceful attacks on their front-line staff and should start talking seriously with the union around an agreement that underpins the guard guarantee and ensures safe, accessible and secure services for all.

“It is the continuing intransigent attitude of the company which means that the industrial action goes ahead in an effort to force them to see sense and to drive them back to the negotiating table for genuine and meaningful talks.

“We know that this action will have a serious impact on services and the responsibility for the disruption caused will be wholly down to South Western Railway and their pig-headed attitude. It is time for the company to get out of the bunker, stop threatening their staff and start talking.”

SWR, which runs services across Southern England, including busy commuter routes to London Waterloo, said it planned to run a normal service over the next four days but advised passengers to check before they travel.