The shocking 32 second clip shows a group of youngsters from Chirk, near Wrexham, standing around another youth seated on a sofa who is set alight after apparently being doused with liquid from a canister.

The youngster then desperately attempts to put the fire out while apparently crying out in pain. At one point another lad shouts: "He's on fire! Put him out!"

The screen then goes dark but the youngster on fire can still be heard apparently crying out as others laugh.

After eventually managing to put the flames out one of the youths, who appears to be filming the scene on his mobile phone, turns to an apparent latecomer and jokes: "You should've seen that."

It is unknown where the footage, which was added to the popular video sharing site just over a month ago, was filmed, though a short description accompanying it refers to 'The Chirk lads in the shed'.

The clip was posted under the category 'comedy.'

The stunt has been condemned by North Wales' senior fire safety manager Richard Fairhead, who claimed the "prank" could have easily turned to tragedy.

"The mental and physical consequences of being involved in a fire stay with you forever, and can cause horrific scarring to both the body and mind," he said.

"What this group of young people see as a prank or a joke could very easily have got out of hand and resulted in the loss of their lives.

"Fire, by its nature, cannot be controlled – a 'laugh' can very easily turn into a tragedy, changing the lives of the victim and all those around him.

"Fires injure many people in Wales every year, and can cause disfigurement and disabilities which irreversibly change the life of the victim."

He added: "To play with fire in this way is totally irresponsible, and these youngsters should realise that the injuries resulting from burns are the most painful imaginable."