PRISON reformers lambasted a demand by Britain’s top cop for tougher sentences for young offenders yesterday, warning that it would lead to more black boys being locked up.

Metropolitan Police Commissioner Cressida Dick called for “harsher and more effective” jail terms for teenagers who repeatedly offend.

In a speech at a Howard League for Penal Reform event, she said some youths were “simply not fearful of how the state will respond to their actions,” citing one 16-year-old in south London who she claimed had committed 42 offences in three years, is involved in gangs and habitually carries a knife, but has never been jailed.

Of the teenagers who are sent to prison, two out of three go on to reoffend within a year of release.

Ms Dick called for a debate about shifting towards stronger sentencing, saying: “It is clear other approaches are no longer working.

“We need to give more real deterrents and we need to use the opportunity that imprisonment could give to better ensure that children — and we must remember they are children — don’t reoffend.”

Howard League for Penal Reform campaigns director Andrew Neilson said: “Cressida Dick was explicitly talking about young black boys. She acknowledged they are frequently both victims and perpetrators, being criminally exploited by gangs.

“The Chief Inspector of Prisons recently said there was not a single institution in this country holding children that could be considered safe. If the answer to this problem is to lock 13 or 14-year-old black boys up for the remainder of their childhood in institutions sometimes described as ‘war zones,’ then that is a counsel of despair.”

The charity’s chief executive Frances Crook pointed out that senior police officers have traditionally avoided commenting on sentencing and punishments.

She said Ms Dick “did not provide a considered understanding of the research and the lived experience of young black (and young white) people in London.”

The Howard League said there was no evidence that making offenders spend more time in prison would work, as knife crime was in decline when mandatory sentences for possession were proposed and adopted in 2015, but it is now on the rise.