There needs to be an "intense police focus" on the minority of young black Britons who are behind a spate of gun and knife attacks, Tony Blair has said.
Mr Blair said ringleaders need to be identified
He said laws on knife and gun-gangs needed to be toughened and the ringleaders "taken out of circulation".
In a speech, the prime minister added that most of the black community were "horrified at what is happening".
But they needed to be "mobilised" in denouncing the gangs killing "innocent, young, black kids", he added.
He was speaking in Cardiff in the wake of a series of fatal shootings and stabbings of teenagers, many of them in London, this year.
He said failing to stop the minority behind crime and anti-social behaviour was the "missing dimension" to an otherwise successful regeneration of towns and cities.
Earlier this month, getting someone to hide a weapon from the police became an offence under a range of measures brought forward in response to the incidents in the capital.
Delivering the Callaghan Memorial Lecture on regeneration, Mr Blair said of the knife-and gun-gangs: "There needs to be an intense police focus on these groups.
"The ringleaders need to be identified and if necessary, taken out of circulation - if very young, as some are, put in secure accommodation."
Mr Blair said the vast majority of the black community are "decent, law-abiding people".
But he added: "We won't stop this by pretending that it isn't young black kids doing it."
The Commission for Racial Equality said people "shouldn't be afraid to talk about this issue for fear of sounding prejudiced".
A spokesman said: "As a society we are failing young black kids. We mustn't place blame but ask why black children are more likely to live in poverty, be excluded from school and be stopped and searched by the police."
But the Black Christian Leaders' Forum said Mr Blair had failed to recognise there were already several church-led initiatives focused on the issue.
"I'm not sure where the prime minister has been, or who he's been talking to, if he thinks black communities have not been denouncing the gangs and gang activity," said Bishop Joe Aldred.
Lee Jasper, advisor to the Met Police's Operation Trident, which tackles gun crime within the black community, said the comments undermined progress made at a recent Downing Street gun summit.
"The black communities of the UK, and London in particular, have for almost a decade been warning government and local authorities that without additional resources for deprived black areas gun crime was going to get worse," he said.