Lone mothers are poorer, more depressed and more unhealthy, says its survey of research into the effects of family breakdown.
"Non-residential fathers have higher death rates, drink more, have more unsafe sex and risk losing contact with their children."
But it is the children who suffer most from these "experiments in living," it says.
Children in fatherless families are more likely to suffer from deprivation and ill-health, unpopularity and exclusion at school. They are also most likely to experience physical and sexual abuse, and to run away from home. They are prone to drinking, smoking and taking drugs, are more likely to become young offenders and to engage in early and unprotected sex.
David Green, director of Civitas, said it was irrational of Tony Blair to insist that family structure was not the business of policy-makers.
"Experiments in living: the fatherless family," by Rebecca O'Neill, is available from Civitas (tel 020 7401 5470) or at www.civitas.org.uk