Government and police strategy for dealing with knife crime is "incoherent" and irrational, according to a study published today.

The effectiveness of tougher sentences and amnesties which were brought in following a spate of recent high-profile stabbings, including several at schools, is not proven, it claims.

Official figures may also be underestimating the scale of the problem, a report by the Centre for Crime and Justice Studies warns.

Researchers from the charity, based at King's College London, surveyed available information on knife crime and the measures put in place by ministers to combat it.

They found a lack of "high quality" and "reliable" data on the nature and number of offences.

However, what evidence existed indicated that a "significant minority" of schoolchildren and young people carried knives and "this problem may be growing".

The researchers concluded: "Although according to official statistics the use of knives in the commission of violent crimes and homicide has remained steady or perhaps even decreased over the last decade, official statistics fail to measure a large amount of violent offences and thus accurately predicting levels is difficult or unreliable."

The report said the most common victims of knife crime were young people, the poor, and racial minorities.

It criticised the authorities for taking a haphazard approach to tackling the issue, and questioned whether tough punishments would have a deterrent effect.