RAIL union RMT reiterated its call for Govia Thameslink Railway (GTR) to be brought into public ownership after chief executive Charles Horton announced his resignation today over severe service disruptions.

The company said Mr Horton will remain in post for a short period to oversee the development of a temporary timetable to address the recent travel chaos, with GTR cancelling hundreds of daily journeys.

The timetable changes, brought in across several franchises at once, have proved problematic, with a severe shortage of drivers on Thameslink in particular.

RMT general secretary Mick Cash said that his resignation would have minimal effect on the way the giant GTR franchise operates as a whole.

The union has been embroiled in a dispute with GTR’s Southern for two years over its plans to scrap safety-critical train guards.

Mr Cash said: “Mr Horton may now have gone but the rotten franchise he was steering remains in place and no change at the top will alter that. This whole basket case operation is a failure on every level.

“His resignation opens the door for this sorry chapter to be brought to a close and that means sweeping GTR away and returning the services to public ownership with safety, access and quality the guiding priorities.”

Mr Horton will be grilled by the Commons transport select committee on Monday.

The committee will also question GTR chief operating officer Nick Brown, rail operator Northern’s managing director David Brown and three Network Rail managing directors.

Martin Abrams, spokesman for the Association of British Commuters, questioned whether Mr Horton is being used as a “fall guy” for Transport Secretary Chris Grayling, who has denied all responsibility for the crisis, despite his department’s role in drawing up franchise specifications.