Prison does not work for young knife-crime offenders, and while stop and search has a short-term benefit, it risks alienating key sections of society, a police study has found.

The study by the College of Policing, the government-backed body aiming to improve law enforcement, has been sent to all forces in England and Wales as they grapple with rising knife crime. It reviewed research on causes and effective strategies.

It found that the peak age for carrying a knife was 15, and said focused “tough” action by police, such as intelligence-led stop and search, can suppress rises in stabbings only in the short term.

The report found that a “public health” approach tackling the root causes was the only long-term hope, involving many other agencies as well as the police.

In an apparent rejection of knee-jerk calls for action, it said gangs were responsible for as little as 5% of stabbings and that tougher sentences and prison did not appear to tackle reoffending.

The report said: “For juveniles (10–18 years), prison alone has been found to significantly increase reoffending, compared to non-custodial sanctions such as community supervision with victim reparation, and community surveillance and aftercare.”

It also said first-time offenders made up the majority – 72% – of those found guilty of knife and offensive weapons offences in the year ending March 2018.

Figures released on Thursday showed that there were 40,829 knife offences across England and Wales last year, up nearly 17,000 since 2013/14.

The study pointed out that young males were the most likely to use knives and that nationwide, “there is no statistically significant relationship between ethnicity and weapon carrying”. But, separately from the study, racial differences have been found across the English regions, with victims and perpetrators in London being more likely to be from African-Caribbean communities. Police in north-west England say they have noted no racial differences.

In London, where one-third of all knife offences took place, African-Caribbeans were more likely to be subjected to stop and search than their white counterparts, to such an extent that more black people were stopped last year than white, despite being a fraction of the population size.

Police have said they carry out stop and searches with respect, but the study warned that the searches can leave people feeling as if they cannot rely on the police to protect them: “While intelligence helps the targeting of stop and search, people’s willingness to provide information is likely to be affected by how fair they perceive the police to be in their use of this power.

“Young people, the economically disadvantaged, and people from some minority ethnic groups are significantly more likely to be stopped, and to be dissatisfied with police treatment during a stop.

“If contact with officers is felt to be unfair, analysis also suggests it can undermine young people’s perception that the police are ‘on their side’, reducing their willingness to comply with the law, and is associated with increased risk that they consider violence to be an option in achieving certain goals.”

Dave Tucker, head of crime for the College of Policing, said: “If you feel you are already at risk and then the police stop and search you and treat you badly, you then feel over-policed and under-protected. You might then decide you will protect yourself because the organs of the state are not doing so.”

The police study said the reasons youngsters carried knives were to protect themselves, especially if they have suffered crime, for “street credibility” and “respect”, and also to carry out crimes such as “theft, sexual assault, injury and serious harm”.

Key risk factors included adverse childhood experiences, such as abuse, neglect, criminality or drug and alcohol abuse by parents, and being in care. Other risk factors include poor school performance and exclusions.

The study said intervention with children typically starts around age 13, and that may be too late. Encouraging results have been achieved by teaching children “social and emotional skills, problem solving and anger management”, better support for parents and after-school activities.

The study concluded: “Public health approaches, involving multiple agencies to develop a range of interventions, including prevention work for at-risk groups, as well as law enforcement activity directed at offenders, have been shown to have a positive impact.”