Couples with young children are five times more likely to split up if they are unmarried compared to those who have had weddings, the Tories claim.
Family splits cause "poverty and other social problems", Tories say
Some 32% of unmarried parents split up before their child is three, a study of 15,000 people recited by the party's Social Justice Policy Group suggests.
The government had tried to "airbrush out references to marriage", group chairman Iain Duncan Smith said.
Labour did not comment on the claims by the former Conservative leader.
The study was written by Bristol-based pro-family campaigner Harry Benson and was submitted to a group set up to tackle problems such as family breakdown, crime and drugs.
Conservative leader David Cameron promised it would "come up with the right policies to help communities to turn themselves around".
'Vital to well-being'
"Family breakdown leads adults and children into poverty and other social problems," Mr Benson wrote.
"Any government that wants to reduce poverty and inequality for both children and adults alike has to address the issue of marriage, and what it is that makes marriages work better than the alternatives."
Mr Duncan Smith claimed the study showed "the government's assumption that children's outcomes are solely dictated by socio-economic factors is wrong".
"The structure within which they grow up and are nurtured is vital to their well-being," he added.
"The government's corresponding attempt to airbrush out references to marriage from family research is a form of censorship."