Cressida Dick, commissioner of the Metropolitan Police, is among those who have suggested that the absence of a father is a factor driving some boys into gangs.

David Lammy, the Labour MP for Tottenham, said that boys needed role models and that “in the absence of a father, young men can draw their masculine identity from their peers”. The former minister, who conducted a review of the treatment of ethnic minorities in the criminal justice system, said that higher paternal absence in some black communities made boys vulnerable. He blamed “colonial slave pathologies” going back hundreds of years.

“There’s a phenomenon in Caribbean communities called baby father — that way of describing your husband comes right back to slavery. It’s basically that he doesn’t own his child, because he could be shipped around. Those issues ricochet down generations, they exist in African-American communities, Caribbean communities and they play out in this country. That’s not an excuse for not parenting your child, or stabbing an individual, but they are important pathologies in families.”

Mr Justice McFarlane said that there was a “crisis of numbers” in the courts as a result of the growing number of children taken into care. “After Baby P, a colleague said it was a tsunami but it wasn’t — the water level has risen,” he added.

Adoptions, however, have fallen by about 20 per cent since a ruling by Sir James Munby, the outgoing president of the family division, that social services must provide “proper evidence” that all alternatives had been considered.

Mr Justice McFarlane said that he supported Sir James’s ruling but insisted it “wasn’t intended to make adoptions go up or down. It was meant to set out for the judges the process of analysis they had to go through.”

The courts should not determine a “correct” number of children being adopted, he added. “We don’t want a particular number of adoptions, high or low; we want the right outcome in the particular case.”

Sir James has called for a reform of divorce law to end blame between couples and the “hypocrisy” of the system. Mr Justice McFarlane said of no-fault divorce: “I am not going to be drawn on that save to say you won’t find a single family judge that is against it.”

The law is evolving, he said, pointing to surrogacy, which is controversial because the woman giving birth is treated as the legal mother and has the right to keep the child. “The law has to provide a structure and solutions for family life. Our understanding of family life has changed radically.”