Details of the government's plan to improve the "life chances" of problem families are to be revealed.
Mr Blair wants to prevent teenage criminality
In a speech, Tony Blair will set out a scheme to intervene before children are even born to stop them turning into troublemakers later.
He is expected to give more details of the idea, which critics say sounds too much like "eugenics".
The prime minister's speech comes during a two-day regional tour which follows his summer visit to Balmoral.
His spokesman said: "If you look at the figures of what happens to children in care and their offending rate, that is quite shocking.
"What the prime minister will be setting out is a way in which we work with those who are socially excluded to try to improve their life chances. That's the key.
"That's why this isn't just about trying to deal with the problem where relatively few numbers of individuals or families are causing disproportionate problems for society.
"It's also about helping those individuals and families improve their life chances."
Last week Mr Blair told BBC News there needed to be earlier intervention, "even pre-birth", with children of "dysfunctional families" and teenage mothers who were not in stable relationships.
'Foetal Asbo fears'
There should be sanctions against parents who refused help, he said.
But he did not explain in detail how the plans would work.
The plans were branded "foetal Asbos" in the media and also came under fire from former Labour Cabinet minister Tony Benn.
"This one about identifying troublesome children in the foetus - this is eugenics, the sort of thing Hitler talked about," he told BBC's Five Live.
Children's charity NCH said Mr Blair must honour his promise to introduce lasting solutions to help the most excluded people.
NCH chief executive Clare Tickell said: "Early intervention will help families break the cycle of exclusion but it must be done in a way that does not stigmatise.
"The government must realise that families need support to change, not to be punished because they are struggling."
The Joseph Rowntree Foundation, which is hosting Mr Blair's speech, called for a balanced approach.
Its director, Lord Best, said: "The underlying causes of many of society's problems can be traced back to child poverty and, although government is making progress, there is still a long way to go to meet the prime minister's pledge to end it by 2020."