Passengers spent almost 10 hours on a stinking overnight bus when toilet water poured into the cabin.

People travelling on the Megabus M11 service from London to Glasgow and Aberdeen were confronted by the issue during their journey yesterday.

However, disgruntled travellers say it is not the first time the problem has happened and are demanding the budget transport firm fix the issue permanently.

Yesterday's trip was so bad that passengers going onwards to Aberdeen demanded another bus when it got to Buchanan Bus Station.

They could no longer stand the smell, having spent more than nine hours on board the vehicle.

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One passenger said the problem is so regular, he has learned to "come prepared" with shoe covers designed for muddy music festivals.

Andrew D'Souza, a 48-year-old health care professional, donned the unusual footwear yesterday during the 10-hour journey.

Frequent passenger Andrew, from the South Side said his bag got soaked in the rancid liquid when he unwittingly left it on the ground and now it "smells like a toilet".

He said: "It's a health hazard, and disgusting.

"Previously the driver blamed other passengers using the toilet but they got an engineer on at Preston last time, who said it wasn't the passengers as it is blue water which is coming out of the tank.

"Once I said they needed to get someone on to mop up the waste and the driver threatened to throw me off the bus - I wasn't being rude, I was being helpful."

Andrew, who was on the bus yesterday, said he has had enough and has urged Megabus to stop running the service using the same buses if they are going to leak.

He said: "Passengers going to Aberdeen yesterday demanded a new bus.

"They agreed to do that in Glasgow, and they gave the passengers all a refund but You shouldn't have to demand this.

"Passengers should not have to revolt for them to see they shouldn't be running a bus covered in toilet water.

"The driver yesterday found a mop in the bus station and just mopped up the water but he doesn't know what that is. He's not an expert.

"There was no concern for health and safety. They didn't even use detergent or anything."

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Megabus denied the issue was a regular occurrence, but admitted there had been other occasions when toilet water had leaked out on the same service.

A spokeswoman for megabus.com said: "This was a very exceptional set of circumstances.

"It does not reflect our normal service and we are very sorry for the inconvenience it has caused our customers.

"We are investigating the cause of this particular issue.

"There have been isolated cases in the past where incorrect use of the toilet by a minority of passengers has impact the travel experience for other customers.

"The problem in this case was reported by the driver at Preston and a replacement coach was ordered, but customers themselves chose to continue on the existing vehicle to prevent a further delay to their journey.

"However, in view of the circumstances, we are providing passengers with a full refund and will also take any further steps required to ensure high quality travel for our customers in the future."