Confused commuters are bringing a multi-million-pound fleet of trains to a sudden halt by using the toilets.

A design problem in South Central's new £850 million Electrostar models, which serve Sussex, means many passengers are confusing toilet flushes with emergency stop buttons.

The problem is just the latest in a series of faults with the trains, which are being brought in to replace the ageing slam-door fleet.

To combat the latest problem, rail guards are being told to give out regular messages advising people on how best to use the toilets to prevent drivers being alerted to stop their journeys.

The problem is caused because a button activating the flush is hidden when the toilet seat is raised in disabled toilets on the new trains.

This means all passengers see is the red emergency button, which many have been pressing, mistaking it for the flush.

That sends a warning to the driver, who must stop the train while guards investigate.

A South Central spokesman said the trains did not have to immediately stop but drivers had to find the nearest safe place to come to a halt.

He added: "The buttons are not next to each other but some passengers are obviously getting a bit confused.

"We are making regular announcements to try to stop it."

South Central has been gradually introducing 700 air-conditioned Electrostar trains and expect them to be in full service next year.

When the fleet was launched in December, the first train out of Brighton broke down on a return trip. Some 33 stations across Sussex have needed their platforms extended because they were too short for the new, longer trains.

South Central has also been threatened with legal action by residents woken up by train horns which are twice as loud as the old variety.

The firm unveiled its Turbostar trains in July but admitted they would be unable to use London Victoria station because their diesel fumes could set of fire alarms.

South Central was bombarded with complaints during the summer because air conditioning on the new trains kept breaking down.

And earlier this month The Argus revealed the carriages of the new fleet are too narrow for buffet trolleys to travel through.