The war between two cut-price bus companies escalated today after one stopped to rescue passengers stranded on its broken-down rival.

Passengers on Stagecoach's heavily-publicised £1 megabus service from Brighton to London were shepherded by traffic police on to a National Express coach after their double-decker broke down on the M23.

Managers at megabus apologised today for a string of mishaps which blighted the service's first weekend trip.

The outward bus had to pull over minutes after leaving Pool Valley at 8.10am because the emergency door would not close. It took a technician 40 minutes to fix.

The return bus left Victoria coach station at 6.45pm but broke down on the M23 five miles from Gatwick.

A replacement bus failed to arrive and at 8.40pm police flagged down the passing National Express coach.

The driver agreed to take the 40 passengers to his destination at Gatwick.

The passengers waited in McDonald's for a replacement Stagecoach bus before eventually deciding to catch a train home shortly before midnight - paying the £3.70 rail fare and arriving home at 12.20am.

Julie Collins, 30, who went on the day trip to London with her father Brian, said: "It was awful."

Julie's father Brian Collins, 57, of Rosebery Avenue, Woodingdean, said: "On the way home it seemed as if the bus was labouring from the outset.

"We got as far as Balham and the bus just about gave up. It just died.

"The driver managed to get it going again and he managed to get us to the junction of the M23 and M25.

"We broke down on the chevrons separating those two roads so we were in a very dangerous position.

"The driver made no attempt to get any communication to the passengers.

"We asked him what was going on after 20 minutes and in a very sarcastic manner he said the bus had broken down.

"It has made me adamant I will never travel on megabus again."

Stagecoach introduced its first Brighton-London megabus service last Monday with a return journey priced at £2.50, including a 50p booking fee.

The same day National Express dropped its return fare from Brighton to London from £9.50 to £2.

Megabus offers a slightly shorter journey time and National Express advertises its on-board loos.

Antonio Natoli, a 23-year-old Italian student from Brighton, was on board the ill-fated megabus.

He said: "No one turned up to take us and no one gave us any information.

"We all felt very angry and decided to complain to at least get the money for the train back.

"I think it showed a serious lack of respect and was absurd and almost criminal to leave a lot of passengers in the middle of nowhere like that.

"I appreciate a bus can break down but it's unbelievable they just left us at Gatwick not knowing what was going on.

"I don't think I'd take a megabus again."

Andrew Dyer, managing director of Chichester-based Stagecoach South, which operates the megabus route, blamed the breakdown on an electrical fault.

He said: "We obviously owe people a big apology.

"We have a number of local coach operators in the outer London area with whom we have a helpline system for rescuing stranded passengers but none of them could help us on Saturday.

"We had to send a coach from our depot in Worthing to pick people up and it took far longer than we would have liked.

"I think people understand mechanical failures can happen but it was unfortunate the back-up systems we had in place didn't work and we will be reviewing those."

Mr Dyer said the company would reimburse people who took the train home.

A National Express spokeswoman said: "After all the coverage they got for their launch, we've had to come to the rescue because they couldn't transport their passengers the whole distance. It has made us chuckle."