The growing reluctance of Britain's twenty- and thirtysomethings to fly the parental nest was revealed today by the Office for National Statistics (ONS) in its annual report on the latest social trends.
It said almost a third of men and a fifth of women aged between 20 and 34 live at home with their parents.
Since 2001, the number of young adults continuing to live in the family home increased by 300,000. The ONS said one reason for young people delaying setting up a home of their own was rising participation in higher education. Another was lack of affordable housing. Graduates carrying a burden of student debt found it harder to pay the rising costs of renting or buying property.
The latest available figures were for the second quarter of 2008. They showed 29% of men aged 20-34 and 18% of women of the same age lived with their parents. This compared with 27% of men and 15% of women in 2001.
The ONS said: "Leaving home is a way of establishing independence and is an important step in the transition to adulthood. However, young adults are tending to stay in the home longer than their parents did.
"A narrowing of the generation gap has led to changing relationships between parents and children, which can make it easier for adult children to remain in the parental home.
"Additionally there has been a large increase in the numbers of students in higher education ... The introduction of university fees in 1997 resulted in some students continuing to live in the family home while studying, or moving away and then returning home afterwards for financial reasons."
A Eurobarometer survey in 2007 asked 15 to 30-year-olds across the EU for the main reason why young adults lived with their parents. In Britain, 44% said lack of affordable housing, 38% said general financial pressure and 12% said they wanted the comforts of home without the responsibilities.
But, as more young adults clung to the family home, there were also more singletons than ever before. The number living alone doubled from 6% of the population in 1971 to 12% in 2008. The largest increase was among people below state pension age, suggesting that the trend was influenced more by separation and choice than by the death of a partner.
The figures showed 237,000 marriages were recorded in England and Wales in 2006 – the lowest number since 1895. The ONS said: "People are generally getting married later in life and women are delaying motherhood."
The average age at first marriage in the UK has risen from 29.3 years in 1996 to 31.8 in 2006 for men and from 27.2 to 29.7 for women. The average age of women in England and Wales at the birth of their first child was 27.5 years in 2007, compared with 23.7 years in 1971.
Other findings included:
• Nearly a third of working mothers in Britain rely on informal childcare provision from the child's grandparents;
• 31% of children in England are being brought up in "non-decent" homes that do not meet a sufficient standard of upkeep, facilities, insulation and heating;
• Nearly a third of two to 15-year-olds in England in 2007 were overweight or obese;
• The number of boys counselled by Childline, the helpline charity, more than doubled from 24,115 calls and letters in 1997-98 to 58,311 in 2007-08;
• One in four young people have been a victim of personal crime and children are the highest risk group for pedestrian and cycling accidents;
• The total distance travelled by people in Britain by road, rail and air increased by 95% since 1971, reaching 817 billion passenger kilometres in 2007;
• The number of adults using internet banking increased from fewer than 3.5 million in 2000 to more than 21 million in 2007;
• The number of penalty charge notices for motoring offences increased from 3.5 million in 1996 to a record 7.8 million in 2006.