The Mayor of London has called for the Prime Minister to help cut violent crime by stopping schools being allowed to unofficially exclude pupils .

These calls come as new evidence suggests children formally excluded from schools or ‘off-rolled’ – pupils simply “disappearing” from school registers without being excluded – are more likely to become involved in or affected by serious youth violence.

Figures show the number of people being permanently excluded from school rose by 40 per cent in London between 2013 and 2017 and 56 per cent nationally.

Calling on the Government to “act urgently”, a letter from Sadiq Khan and police chief constables across the country said: “The practice of off-rolling must be outlawed.”

“Clearly, the way the education system deals with excluded young people is broken. It cannot be right that so many of those who have committed offences have been excluded from school or were outside of mainstream education.

“Time and again we are hearing how the fragmentation of the education system, and the breaking of the link between schools and local authorities, has led to a lack of accountability, coordination and action.”

The letter also asks for the Government to give local authorities more powers over school exclusions and more funding to help vulnerable people.

A report from 2017 by education watchdog Ofsted said schools ‘off-rolling’ pupils was in the interest of the school rather than students.

Mr Khan suggested schools do it to “boost performance” in exam league timetables.

Research by HM Inspectorate of Prisons also shows that nine out of 10 children in custody have been excluded from school.

The chairman of the London Assembly police and crime committee, Steve O’Connell, said: “We must do all we can to combat youth violence and attack it from all angles.

“Bringing the number of exclusions down and supporting those at risk of exclusion would be a key tactic in prevention.

“One young death to violent crime is one too many. All parties who have a hand in building the future of a young person have a duty to make sure they reach their destination and are not stopped before their time.”