The minister in charge of a plan to identify potential troublemakers even before birth has defended the move, saying state intervention "can work".
Earlier intervention is necessary, ministers say
Social exclusion minister Hilary Armstrong spoke out as ex-MP Tony Benn likened the plan to "eugenics, the sort of thing Hitler talked about".
Ms Armstrong says the government has to intervene earlier to prevent problems developing when children are older.
Tony Blair will outline the strategy in a speech in the regions on Tuesday.
The prime minister says it is possible to spot the families whose circumstances made it likely their children would grow up to be a "menace to society".
He said teenage mothers and problem families could be forced to take help to head off difficulties.
His government has made "massive progress" in tackling social exclusion but there is still a group of people with multiple problems, he said.
There had to be intervention "pre-birth even", he said, because families with drug and alcohol problems were being identified too late.
And he conceded many people might be uneasy with the idea of intervening in people's family life but said there was no point "pussy-footing".
But he said: "If we are not prepared to predict and intervene far more early then there are children who are growing up - in families which we know are dysfunctional - and the kids a few years down the line are going to be a menace to society and actually a threat to themselves."
Mr Blair will hammer home his thinking on Tuesday in his first policy speech since his summer break.
But Mr Benn, an MP until 2001, dismissed the plan as one of "a million new gimmicks" outlined by the prime minister.
"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.
"I just think that people don't believe him any more."
But Ms Armstrong said while the government had raised "many, many people out of dire poverty and worklessness" it now needed to give them "the ability to see what they can do to raise their children's opportunities".
"There is a group at the bottom that no government has previously effectively tackled and we are now taking the next step," she told Andrew Marr on the BBC's Sunday AM programme.
"I know that they do have aspirations for their family. They too would like their children to being doing very well.
"For some they have not had the experience, they have not had the role models ...
"If we can find what it is that will really tap into them, then we can really change their belief in themselves and their ability to cope with the world."
Ms Armstrong said she had spoken to the partner of a drug addict at the NCH Bolton Families project which supports families who are at risk of eviction due to anti-social behaviour.
She told the minister that he would not have been receiving treatment if he had not been pushed into it.
"We know that intervention can work," said Ms Armstrong. "I'm bringing out a new action plan in the next few days."
Clare Tickell, chief executive of the children's charity NCH, said: "There is no doubt there are families who need support. Some children are being brought up in a family whose needs are so complex that they are struggling to function.
"Early intervention can break this negative cycle of behaviour for good and prevent the children of struggling parents today being the struggling parents of tomorrow."
However, the Conservatives argue that the answer is "not more state intervention", while the Liberal Democrats claim the government has failed to tackle poverty, crime and social exclusion for the last nine years.
Anastasia de Waal, head of the family and education unit at think tank Civitas, said: "It is teetering on genetic determinism this kind of saying that before children are even born they are labelled as problematic."