The ONS found 25 per cent of 20 to 34-year-olds, about 3.4 million people, still lived with their parents in 2018, up from 21 per cent in 1996.
Men were most likely to stay at home with almost a third living with their parents, compared to 20 per cent of women in the same age group.
The number of cohabiting couple families has continued to grow faster than married couple and lone parent families, with an increase of 25.8 per cent between 2008 and 2018.
The number of same-sex couple families has grown by more than 50 per cent since 2015, with more than four times as many same-sex married couple families in 2018 compared with 2015.
There are also a record number of people living alone. About 8 million people now live on their own – around 15 per cent of households – up from 7.7 million in the previous year. These figures are driven by increases in women aged 45 to 64-years-old and men aged 65 to 74-years old.
Andrew Montlake, managing director of Coreco, said the figures were a damning indictment of the property market today.
“Rents have soared, especially in major cities, while the first rung of the property ladder is out of reach given the sizeable deposits now required,” he said.
“In the capital, only young people with high paid jobs and easy access to the Bank of Mum and Dad have got a chance of owning a home. And that’s after the price falls of recent years.”
He added: “For 3.4m young adults to be living with their parents is proof positive that the property market, despite the policies and initiatives of numerous governments, is fundamentally broken.”
Saddled with debts
Sarah Coles, personal finance analyst at Hargreaves Lansdown, said young people were likely to remain in the family home for a variety of reasons, but finances were critical.
“They’re likely to stay in education or training for longer, and the cost of study away from home is encouraging more of them to stay put,” she said.
“Those who do uproot themselves for their studies are more likely to boomerang back home afterwards – saddled with debts and unable to stretch to the soaring cost of getting a place of their own.
“Men are more likely to live alone in mid-life because more men than women choose not to marry. When they do get married, they do so at older ages, and when couples break up, men tend to live alone.
“Women are more likely to be alone in retirement, because their husbands are typically older and women tend to live longer, so more women are widowed,” she added.