Children as young as six require intervention from the authorities to stop them becoming involved in gangs and gun crime, the PM has told the BBC.
Police have been handling a spate of shootings recently
"Specific measures" were needed for a "specific number of families who are just outside the mainstream", he said.
Tony Blair was speaking after a No 10 gun crime summit at which plans were outlined for tougher punishments and more funding for community groups.
But community groups said legislation alone would not solve the problem.
The summit with police and community leaders follows a spate of fatal shootings involving young people.
Speaking from Liverpool, where he had been visiting a community justice project, Mr Blair said: "You've got to intervene very early with these children, sometimes aged six or seven you can tell that these children are going wrong."
The intervention should come "not necessarily from central government" but from "here in the local community", he said.
"For this specific number of families who are just outside the mainstream of society you need very specific measures."
And he said help could come from "within these communities" with initiatives like reformed gang members talking to youngsters.
Earlier, speaking outside Downing Street after the gun crime summit, Home Secretary John Reid confirmed tough punishments for those who use other people to look after weapons.
Mike Todd, chief constable of Greater Manchester Police, had told the conference children as young as 13 had been found with firearms which they had been asked to hide for others.
Other plans include more funding for community groups and making gang membership an aggravating factor in sentencing.
Mr Reid also announced a review of the legislation on gangs, guns and knives at the meeting of community leaders and crime experts.
The review will cover sentencing policy - including that involving juveniles - gun supply and gang membership.
Mr Reid said he would also "lay an order or any orders that are necessary" to make sure a minimum sentence for a gun offence "truly is a minimum sentence" even for those aged 18 to 21.
The number of people injured by firearms in England and Wales has more than doubled since 1998
In 2005/2006, the number of gun murders fell by more than a third from 78 to 50
There were 11,084 recorded firearms crimes in 2005/2006 - up 0.12% on previous year
London, Greater Manchester and the West Midlands account for 54% of recorded incidents
Source: Home Office
Although a five year minimum was introduced in January 2004, the appeal court found last March that because of a clash with separate legislation it could not be applied to those under the age of 21.
Gun crime in the UK is still rare with 50 deaths in 2005/2006 compared with 78 the year before.
But the number of recorded gun crimes in the UK rose to more than 21,500 last year compared to just under 14,000 in 1998.
A number of community leaders attending the meeting warned that Britain was in danger of creating a generation of "urban child soldiers" and said young people needed to be offered an "exit strategy".
Rev Nins Obunge, of the churches group Peace Alliance, said changes in legislation would not help support young people "who need an exit strategy".
Shadow home secretary David Davis welcomed "the sentiment from the home secretary".
"But where is the action on family breakdown, truancy and stopping drugs and guns from coming into the country through our porous borders?," he said.
There have been five fatal shootings in London in the past month, three of which were of teenagers in the south of the city - two of them killed in their own homes.
Hundreds of people gathered in south London at dusk on Thursday for a "prayer walk" - organised by a coalition of black churches - through the boroughs of Southwark and Lambeth, both blighted by recent killings.