The Mayor of London and the council leader have written a joint letter to a rail company over their concerns over train disruption during Brighton Pride.

Govia Thameslink Railway (GTR) confirmed that no trains will run to and from Brighton next Saturday, which will coincide with the busiest day of the city’s Pride festivities.

The company has cited safety concerns due to an overtime ban by rail union Aslef for the decision to suspend services.

In the letter to GTR, London Mayor Sadiq Khan and Brighton and Hove City Council leader Bella Sankey called on the company to work with all partners to ensure a safe and successful Pride and maintain connectivity between the two cities.

They said: “Any possibility that GTR would not run any services into Brighton’s mainline station from the surrounding region would have a disastrous impact on the safety and success of Pride. It would also deeply undermine your reputation as a company committed to the LGBTQI+ communities.

“It is incredibly important that day travellers on Saturday, August 5, are able to arrive and leave our cities in a safe, appropriate and managed way. Your trains are an essential part of that you have a huge responsibility to ensure our cities are not cut-off for one of its most important LGBTQI+ events of the year.

“I understand that your position is that the service cannot be operated due to Aslef’s ongoing overtime ban. However, I understand Aslef believe the service could still run by making adjustments to staffing rotas.

“We are asking that GTR urgently work with Aslef and other partners to explore all possible options to ensure the availability of a full schedule of transport to and from our cities on Saturday, August 5.”

GTR said that the “extremely difficult decision” to cancel train services had been made “with a heavy heart” due to safety concerns.

Chris Fowler, network operations and performance director for GTR, said: “After exploring all possible options, and following discussions with the police, emergency services and local council, we simply cannot run a safe service with enough capacity for the extraordinary number of passengers that travel to Brighton for Pride.

“We cannot in good faith bring people into Brighton that cannot get home again, potentially leaving thousands of people stranded - safety must come first.”

Trains on the Brighton mainline will terminate at Three Bridges on August 5, with stations between Three Bridges and Brighton not being served all day.

Services will also not run along the southern coastways to Brighton due to an amended timetable that will be in place.

Customers who had been due to travel will be able to claim refunds, with details available on the rail company’s websites soon.

Train services on Friday, August 4 and Sunday, August 6 are unaffected by the cancellations.