One in four children of cohabiting parents suffer family breakdown before they start school at the age of five, researchers have found.
This is compared to just 1 in 10 children of married parents who experience a divorce or separation by this same stage.
Findings are from the Millennium Cohort Study (MCS), which is ongoing since June 2001, monitoring 15,000 children since birth. It is one of the largest surveys on family life to date.
MCS researchers comment: “There is clear evidence that whether or not their parents were living together at nine months and whether or not their parents were married to each other at this stage affects children’s likelihood of experiencing family change in their first five years of life.
“The experience of family change or living apart from natural fathers can be associated with negative outcomes for children.”
Robert Whelan of think-tank Civitas said “The strong implications for governments is that they should be doing more to support marriages.”
Experts say that children born outside of marriage are more likely to do worse at school, suffer poorer health and face problems of unemployment, drugs and crime.
Teachers warn that breakdown in the family unit leads to a decline in school discipline.
Earlier this year Phil Whalley, a secondary school teacher, told delegates at The Association of Teachers and Lecturers that children coming to school angry and upset because of a chaotic home-life were often unable to learn.
Cohabitation contributed to the problem, he said, with unmarried couples twice as likely to separate as their married counterparts.
Recent research compiled by the University of Essex found that 44 per cent of babies are now born to unmarried parents. Cohabitees are estimated to make up three-quarters of those parents.
John Ermisch, Professor of Economics at the University of Essex, said: “The instability of these unions means, however, that more British children will spend significant parts of their childhood in families with only one parent – and this appears to have long-term negative consequences.”