The investigation found films showing children as young as 11 and 12 punching and kicking other youngsters.

Brandishing handgun

One showed a youth brandishing a handgun and smashing it against a police car.

Another shows a laughing teenager jumping on a police car and shattering its windscreen.

Deputy Chief Constable Brian Moore, of the Association of Chief Police Officers, said it was the responsibility of internet companies to search their sites for videos of violence and crime.

They should then pass the details to police.

He said: "They are responsible for what is on their products - they are making a profit from this.

"We would question who is in a financially better position to police the likes of YouTube - those in the private sector, who are earning huge amounts of money, or police forces which are currently having to stretch budgets."

But YouTube, said it did not employ anyone to police what is posted. The site, which is owned by Google, claims pre-screening content is a form of censorship which is not the role of a private company.

A spokesman said the website takes down videos but only if they are flagged by users and subsequently found to breach their guidelines.

Rule breakers

"Sadly as with any form of communication, there is a tiny minority of people who try to break the rules," the spokesman said.

"On YouTube these rules prohibit content like pornography or gratuitous violence. We don't want that sort of material on our site, and nor does our community."

The YouTube spokesman added the website would help police if they were approached for information.

Another website which features in the programme, Liveleak, said it checks all videos before hosting them.

Hayden Hewitt, co-founder of the website, defended the inclusion of such fights including one in which a girl had to go to hospital with a detached retina.

He said: "Of course it's horrible. It's not about me morally defending anything here.

"We have to take a stance of saying 'look all this is happening, this is real life, this is going on, we're going to show it."'

Panorama: Children's Fight Club will be shown on BBC One on Monday, 30 July at 2030 BST.

Have you been affected by any of the issues in this story? Have you been a victim of violent video footage? Do you think YouTube should monitor what is posted on their site? Contact us using the form below.