The national knife amnesty has had a "negligible effect" on stabbings and knife point robberies, according to experts.

During the five-week amnesty, which ended on June 30, 1,838 potentially lethal weapons from Samurai swords to pen knives were handed in at Oxfordshire police stations.

But more research should be carried out into the effects of the amnesty, according to a report published yesterday by London's Centre for Crime and Justice Studies. The report Knife Crime: Ineffective Reactions to a Distracting Problem? stated: "Little is known about who is likely to hand in a knife during the amnesty, or why. It is likely, however, that those people who routinely carry a knife for protection or intend to use a knife in crime will not be safely disposing of their knives in the bins provided at police stations."

Supt Liam Macdougall, of Thames Valley Police's local policing unit, said: "(The amnesty) was successful but it is not a complete answer to knife crime, and I don't think anyone ever thought it was.

"I think the most effective way of stopping knife crime is to change the culture around it."

He said increasing education about the dangers of knives were vital.

The report also criticised Witney MP and Tory party leader, David Cameron. It stated: "David Cameron's comment that rap music encourages the carrying of knives shows a lack of understanding of the reality of the problem."