The News of the World said senior defence ministry officials confirmed the authenticity of the fuzzy video, taken in May at Bickleigh Barracks near Plymouth, southwest England, home to the elite 42 Commando unit.

"This is the worst thing that I've seen happen -- that's why I filmed it -- but it's the tip of an iceberg," said the newspaper's source, described as a Royal Marine veteran of Afghanistan and Iraq.

The video -- aired later on British news programmes -- purportedly shows a non-commissioned officer in a blue surgeon's outfit leading the abuse.

At one point the NCO is seen kicking a recruit unconscious.

The newspaper's source said recruits were subjected to electric shocks to their genitals, forced to crawl naked through thornbushes, and urged to fight one another with one hand tied behind their backs.

A Ministry of Defence spokesman said an investigation had been launched by the Royal Military Police's Special Investigations Board.

"The Royal Marines take these allegations extremely seriously and have a zero tolerance policy on bullying and harassment," he added.

"Because of this ongoing criminal investigation, we are unable to comment on the details behind these allegations.

"Bullying and harassment is not widespread within the armed forces. Behaviour of this kind will not be tolerated and every effort is made to apply this policy rigorously.

"Whenever there is a proven breach in this policy we always take appropriate disciplinary action."

Colonel Bob Stewart, a former commander of British forces in Bosnia, said he was appalled by the footage and believed it would also shock commanding officers at 42 Commando.

He told BBC News Online the activity was "clearly booze-fuelled" and condemned it as "absolutely wrong and horrific".

Patrick Mercer, the main opposition Conservatives' spokesman on homeland security, told the same site he had encountered similar activity during his 26-year army career.

"I can't tell you how damaging it is," he said.

His colleague Michael Ancram, the Tories' defence spokesman, described it as "inexcusable" while Timothy Garden, a former assistant chief of defence staff, said bullying and abuse needed to be stamped out.

"If new recruits are bullied as they train, you can link that to abuse in Camp Breadbasket and so on," he said, referring to British soldiers' proven ill-treatment of Iraqi detainees in the southern city of Basra.

Another video of apparent bullying was unearthed in September while there has been a long-running campaign into claims of abuse at the Deepcut barracks in Surrey, southern England.

Four young soldiers died there from bullet wounds between 1995 and 2002. Their families maintain they were bullied and question the official army report that they committed suicide; one of the soldiers was shot five times.

A report by British lawmakers in March this year condemned the army for failing to properly tackle the issue, leading to "a tolerance of, or at least insufficient action being taken against, bullying".

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