THE rail safety regulator should “urgently intervene” in the row over guards on trains, union reps said yesterday after a passenger fell through the gap between a train and a station platform.

After getting off a late-night Southern train at East Croydon last month, a passenger walking along the platform descended onto the track.

The driver and platform dispatch staff did not see the accident, but the “on-board supervisor” — the new job title given to former guards on Southern — noticed it and took action.

The passenger was unhurt and was left in the care of British Transport Police officers while the supervisor was put under “verbal pressure” to get the train moving, rail union RMT said.

A row between RMT and Southern over the role of guards has become one of the longest-running industrial disputes in transport history.

Southern has imposed driver-only operation on all its trains, a measure that unions fear will compromise safety, disability access and jobs.

On-board staff on Southern will walk out again next week. Guards on Merseyrail, Greater Anglia, Northern and South Western Railway are also to strike over similar concerns on those networks.

RMT said it suspected Southern had “covered up” the October 20 incident as train drivers in the Aslef union are being balloted on a deal to end their own dispute with Southern.

Aslef says it has made significant progress in talks and its deal will guarantee that there is a second member of staff on trains in all but a few “exceptional” circumstances, but RMT has criticised the proposed resolution.

Now RMT general secretary Mick Cash has written to the Office of Rail and Road (ORR) demanding a “full and thorough investigation” of the East Croydon incident.

Mr Cash said it was “pure luck” that an on-board supervisor who had received the training previously given to guards was on the train.

“This is just the latest in a catalogue of incidents that proves that the Southern plan to hack back on safety competencies and run a growing number of [driver-only] trains is a lethal gamble with passenger safety,” he said.

A Southern spokesman said: “We reject this completely. We assign an on-board supervisor to every train where we previously had a conductor and they are all trained to act quickly and appropriately in situations such as this — all on-board supervisors would have acted in the same way.

“Furthermore, trains at East Croydon are dispatched by platform staff. They would have checked the length of the platform before telling the driver it was safe to leave.”

An ORR spokesman added: “We are aware of the incident and are making preliminary inquiries.”