The Metropolitan police are planning to increase the number of officers working full-time in schools in London, as concerns grow about a surge in knife crime.

Deputy assistant commissioner Mark Simmons told an inquiry into knife crime there were 420 police officers with full-time roles in schools in the capital – up from 280 12 to 18 months ago – and that the aim was to get the total up to just under 600.

The use of officers in schools, though supported by many headteachers, has been seen as controversial because of concerns about the appropriateness of police in an education context, potentially gathering intelligence on young people.

Simmons, who was being questioned by MPs on the cross-party education select committee, said the aim of having more officers in schools was to develop better relationships and improve engagement between young people and the police.

Asked about stop and search, he said it was an important tool, if used in the right way, to increase safety and reduce the likelihood of a young person carrying a knife.

“We are investing heavily in more officers working full time in schools. We have gone from 280 or so 12 to 18 months ago to 420 officers full time, and our ambition is to get to just under 600.

“We need young people to see the police not just as the person who stops them in the street and searches them, even though that may be an absolutely proportionate, legitimate thing to do, but also as someone who can become familiar to them, who can be approachable, who can engage with them day to day within school. It’s a really important part of our approach.”

He said police were also offering a “schools watch” programme, providing safe routes for pupils making their way home after school between 3pm and 6pm, when young people are known to be particularly vulnerable. So far, 78 schools in London have taken up the offer and 40 have turned it down.

The deputy assistant commissioner was giving evidence at a one-day inquiry into knife crime by MPs on the education select committee. Also giving evidence was the former Ofsted chief inspector Sir Michael Wilshaw, who said stop and search had to be used sensitively because it alienated some groups in society.

“Most headteachers I know would stop and search a youngster they suspect of carrying a weapon.” As a headteacher, however, he said he had resisted using knife arches and metal detectors because he did not want schools to be “prison-like”.

A key focus of the inquiry was a possible correlation between the recent increase in the number of pupils being excluded from school and an increase in knife crime. According to official figures, there were 7,700 permanent pupil exclusions in 2016-17, the equivalent of more than 40 a day during the school year, up from a little over 35 a day the previous year.

Quick Guide Knife crime in the UK Show What is the scale of the problem? Police chiefs have described the recent spate of knife crime as ‘a national emergency’. In the first two months of 2019 there were 17 homicides in London alone, where 35% of all knife crimes are committed. The number of NHS England admissions among people aged 10-19 with knife wounds has risen 60% in five years, surpassing 1,000 last year. The number of knife and offensive weapon offences in England and Wales have risen to their highest level for nearly a decade, with the number of cases dealt with by the criminal justice system up by more than a third since 2015. Knife crime-related offences recorded by the police rose by 8% in England and Wales in 2018. Figures on sentences handed out for such crimes, published by the Ministry of Justice, showed there were 22,041 knife and weapon offences formally dealt with by the criminal justice system in the year ending March 2019. This is the highest rate since 2010, when the number was 23,667.

What happens to people caught with knives? In the year ending March 2019, 37% of knife and offensive weapon offences resulted in an immediate custodial sentence, compared with 22% in 2009, when the data was first published. The average length of the custodial sentences rose to the longest in a decade, from 5.5 months to 8.1 months. Are younger people more at risk of being involved in knife crime? The MoJ figures revealed that the number of juvenile offenders convicted or cautioned for possession or threats using a knife or offensive weapon increased by almost half (48%) between the year ending March 2015 and the year ending March 2019. The increase in adult offenders over the same period was smaller, at 31%. However, adult offenders still accounted for 74% of the total increase in cautions and convictions received for those offences in that period. What are the government doing about knife crime? In March 2019 chancellor, Philip Hammond, handed an extra £100m to police forces in England and Wales after a spate of fatal stabbings led to a renewed focus on rising knife crime and police resources. In the same month more than 10,000 knives were seized and 1,372 suspects arrested during a week-long national knife crime crackdown. Officers carried out 3,771 weapons searches, during which 342 knives were found. Another 10,215 were handed in as part of amnesties.

A new Offensive Weapons Act was passed in May 2019, making it illegal to possess dangerous weapons including knuckledusters, zombie knives and death star knives. It also made it a criminal offence to dispatch bladed products sold online without verifying the buyer is over 18.

Many of the witnesses agreed that being excluded increased a young person’s vulnerability to crime. Carlie Thomas, a senior caseworker for the St Giles Trust, working with young people caught up in crime and exploitation, said: “The fact is that our young people, when they are in school, they are not on the roads.

“That’s seven hours of keeping them away from risk, keeping them in a safe and secure place where they are able to find help if they need help. When our young people are excluded from the education system, that’s another life you could lose. The minute they are excluded, they are at risk.”

Wilshaw said on the rare occasions he had excluded pupils as a headteacher, he was often “committing them to a miserable few years afterwards. We realised very quickly even if they went to a decent pupil referral unit … they were in great danger of being drawn into crime.”

He said he believed school funding cuts had led to an increase in exclusions. Previously, schools would have been able to afford to run a therapeutic or learning support unit on site for challenging pupils, who would not have to be excluded. “I could not afford that facility now,” said Wilshaw.

The former Ofsted chief also raised concerns about the role of local authorities in monitoring school exclusions. He said council oversight of schools had been marginalised with the introduction of autonomous academies, and many were now reluctant to challenge academy trusts.

“I’m not sure local authorities know what is happening in schools, and particularly in schools that are not their own, academies and free schools, and feel wary of intervening with very powerful chief executives.

“There has to be a better balance, and local authorities need to have a part to play in monitoring what’s happening in all their schools, including academies and free schools.”