Passengers watched in shock as their train came off the rails as it pulled into a station.

The South Central service from Brighton to West Worthing had already been cancelled because of a fault and should not even have had any passengers aboard, the rail operator has admitted.

The new Electrostar 377 was rolling into sidings about 400m from Brighton station when the accident happened on Wednesday at 10am .

Although the only three commuters on board escaped injury, it is another embarrassment for bosses given the task of modernising the ailing railway service.

All services from Brighton were running about 20 minutes behind at lunchtime on Wednesday as a result of the derailment.

A spokesman for South Central said: "The 9.40am Brighton to West Worthing service was cancelled because of a fault on the train.

"It was being sent back to the depot but unfortunately about three people were on board.

"We found them on the train when it got back to the depot, so we sent them back, and it derailed a quarter of a mile from the platforms in sidings.

"The power was turned off at 10.59am and restored at 11.16am.

"The passengers were put on taxis and sent to their destinations.

"No one was hurt and the train is fine."

The accident is the latest in a string of troubles for South Central since the first of its £856 million fleet of Electrostar 377 trains entered regular passenger service in December.

The company's 736 new units, introduced to replace its 40-year-old slam-door trains in Sussex, had to be modified after trial runs showed closing carriage doors could cause delays.

The distinctive green and yellow trains come complete with air conditioning, comfy seats, smart white tables and boast a top speed of 100mph.

However, one off the first new trains broke down on its fourth journey from Brighton to Seaford due to a technical fault.

In January, the company revealed taxpayers would have to stump up for a delay in bringing hundreds of the trains into service when it emerged a power shortage from the rail lines meant they could remain out of action until 2006.

South Central said the incident on Wednesday would be formally investigated.