Talks aimed at resolving the dispute over the role of conductors on Southern rail services have broken down.

The Rail, Maritime and Transport union (RMT), which staged three days of strikes over the issue last week, claimed the operator rejected a proposal that would have ensured the role delivered by a second person on a train in addition to the driver.

The union's executive is to consider its next move this afternoon.

RMT general secretary Mick Cash said: "We had a golden opportunity in these talks to make some serious progress on the core issue of a second person on the train who would have protected the safety of passengers, delivered customer service and ensured access to services for those with disabilities or needing assistance.

"It's a bitter blow that a firm set of union proposals that could have allowed us to move forward were rejected out of hand. The matter will be discussed by the union executive this afternoon."

Talks aimed at resolving the row broke down at the conciliation service Acas on Monday morning.

Govia Thameslink Railway (GTR), the parent company of Southern, vowed to press ahead with its modernisation plans after an agreement could not be reached.

Angie Doll, the firm's passenger services director, said: "We have been talking to the union for nine months now and, despite several visits to Acas, the union won't agree a deal.

"Passengers will be rightly exasperated that the RMT won't agree to what most fair-minded people would believe is an incredibly good offer.

"We are guaranteeing jobs, pay and a second person on as many trains as we do today and also offered to work with the RMT to agree modern working practices to reduce cancellations and passenger disruption."

She added that drivers have safely operated train doors on services across Britain "day in, day out for decades", and claimed that this dispute is "purely about union power and control".