Former hacker Adrian Lamo has claimed to be the source who informed on a US soldier accused of sending the Wikileaks whistleblowing site video footage of a helicopter shooting unarmed Iraqi civilians.

According to Lamo, US Army 10th Mountain Division specialist Bradley Manning contacted him via instant messaging as a would-be ally, admitting responsibility for the video leak, which is reported to have included scores of other classified files.

"At the moment he gave me the information, it was basically a suicide pact," Lamo is reported to have told the BBC, before justifying turning informant on a mixture of personal and national security grounds.

"I was worried for my family - that if I were obstructing justice that they could be caught up in any investigation. I wanted to do this one by the book, by the numbers. I didn't want any more FBI agents knocking at the door," Lamo said.

Twenty-two year old Manning was arrested by the US military on Monday and is currently being held in ‘pre-trial confinement’ in Kuwait.

The video Manning stands accused of handing to Wikileaks can be viewed here, and relates to an incident from July 12 2007 during which an Apache gunship tracked and killed twelve people on the ground, including two Reuters journalists.

Lamo’s claimed actions have split opinion between those who consider he had no choice given the national security and legal implications of what he was told, and others - the majority - who have branded him an unprincipled ‘snitch’.

Regardless, Lamo seems unrepentant and defiant, which could only attract even more ire.

“I hope you get hit by a car. No, a bus! No, a train!,” one website poster commented, to which Lamo answered, provocatively:“You show a remarkable disregard for civilian casualties.”

Another post laid into Lamo: “Your asperger's really has made you one f***** up, cold heartless human...” to which Lamo replies “Can I use you as a reference on my c.v.?”

The US military has had several run-ins with the Wikileaks site and was reported earlier this year to have considered ways to counter and undermine its credibility.