The number of young adults living with their parents has increased by a quarter since 1996, official figures show, with high house prices and growing youth unemployment forcing many to remain in the family home.

A total of 3.3 million 20- to 34-year-olds lived with their parents in 2013, according to the Office for National Statistics, the highest number since it started keeping records in 1996.

Over that period the number of young adults sharing a home with their parents rose by 25%, despite the proportion of the population aged between 20 and 34 remaining broadly the same.

The ONS data showed that people were most likely to live with their parents in their early 20s, with 49% of 20- to 24-year-olds in the family home, compared to 21% of 25- to 29-year-olds, and 8% of 34-year-olds – and it is the percentage of the youngest age group that has increased most noticeably, rising from 42% in 2008.

Young adults have been hit hardest by unemployment in the downturn, and the figures suggest this has been a factor behind increasing numbers staying in the family home. Between April and June 2008, 13% of the economically active population aged 18-24 was unemployed, a figure that had increased to 19% by the same period of 2013.

The percentage of unemployed people who live with their parents (13%) is more than twice that (6%) of those who live independently.

The increase in the number of young adults living with parents also coincides with a period in which house prices rose relative to incomes. In 1996, the typical first-time buyer had to raise 2.7 times their salary to afford to buy a home, but by 2013 the figure stood at 4.47. This, combined with stricter mortgage criteria and rising private rents, is likely to have driven more young adults back to the family home.

Matthew Pointon, housing economist at Capital Economics, said it was no surprise the increase had coincided with the economic downturn.

"The recession hit the young particularly hard, with a sharp rise in youth unemployment. Furthermore, there was a collapse in the availability of mortgages for buyers with small deposits, which prevented many would-be first-time buyers from flying the nest," he said.

"With lenders demanding a deposit of at least 25%, and with savings rates at record lows, many young buyers desperate to get on the housing ladder would have seen staying with their parents a little longer to boost their savings as their only option."

Matt Griffith, an associate fellow at the IPPR thinktank who has written on housing policy, said the figures highlighted a political failure in dealing with housing. "Short-term recession-related unemployment is colliding with long-term housing failure to create intense pressures on young people and their housing choices. We are seeing a regression towards much less mobile households as a result," he said.

"Unfortunately, up until now, the policies we need to address this – much greater levels of housebuilding and reining in excessive housing demand – are seen as upsetting that more powerful generational political force: older voters. The silver lining is that housing costs are now so absurd we are starting to see a recognition across all groups that things really do need to change."

Neil Hudson, associate director of residential research at estate agency Savills, said the housing market was already working against young people before the downturn began. "First-time buyer numbers started to drop-off in 2003 suggesting that by that point the market was beginning to get a bit too expensive for many younger people; it was at that time that the buy-to-let sector really began to rise too," he said. "We also saw younger people starting to come out of university with more student debt." Hudson said parents who were able to put up their adult children were acting as a "pressure valve" on the rental sector, where the average cost of housing is more than £800 a month. "People can think 'I may lose a bit of my social life but I will save a lot of money if I move back in with my parents'," he said.

The ONS said that in 1996, the typical first-time buyer had to raise 2.7 times their salary to afford to buy a home, but by 2013 the figure stood at 4.47.

Campbell Robb, chief executive of the housing charity Shelter, said the figures wouldn't be a surprise "to the thousands of hard-working young people still living in their childhood bedroom". He added: "The government already knows that it needs to meet people halfway and give hard-working young people the chance to put down roots in a stable home of their own. Now it has to get serious about the chronic shortage of affordable homes and make building a priority, rather than pumping more taxpayers' money into mortgage guarantee schemes."

Christine Northam, a counsellor at the advice charity Relate, said the change was also putting pressure on parents who had expected their children to move out when they went into higher education. "It's a role change, people may have to learn to cope with living with an adult child. If the couple aren't very good at adapting it can be difficult," she said. "Couples who had held on for the sake of the children find that they are holding on for longer."

A breakdown of the figures along gender lines showed that for every 10 women aged 20-34 who lived with their parents in 2013, 17 men did so. The ONS said this substantial difference could be explained by looking at the living situations of young adults.

"In the 20-34 age group, over 600,000 more women than men were living as part of a couple in their own household," it said. "The main reason for this is that, on average, women form partnerships with men older than themselves. Thus more women than men in this age group were married or cohabiting."

In addition, 589,000 more women than men were lone parents in their own household, and women were more likely to take part in higher education than men, leving the family home to do so.

The ONS also compared UK data with figures from Europe, and said that in many EU countries young adults were more likely to live with their parents.

In the UK, 15% of 25- to 34-year-olds are in the family home, and the proprtion is lower in just six of the 28 countries of the European Union. In Denmark the figure was just 2%, but in Croatia it reached 68%.

Case study

Katrina Parmiter, 26, and her fiance Harry Orford, 25, moved in with his mother, Maxine, and two younger sisters last August after living together in a rented home. Their plan was to save up for their wedding this July and for a home.

It has not gone quite as they hoped, says Katrina: "Sadly, a good portion of our income seems to go on outings and activities to keep us out of the house. It's not as though we don't all get along – they are fabulous and so welcoming – but the adjustment from our own space to someone else's has been more difficult than anticipated."

Katrina, an accountant, says it has been hard to get used to using someone else's things after time in her own home, and that she feels much more obliged to wash up quickly and be tidy. "Basically, I miss the opportunity to be lazy," she says.

The couple pay rent and contribute to food bills, and have put their furniture in storage, so they are still a way off raising the money to buy in Bridport, Dorset, which has been dubbed "Notting Hill on Sea" because of its popularity with London buyers.

"Not a lot of property comes on the market here for under £200,000," says Katrina. "There are a lot of people who I went to sixth form with who just can't afford to live here." She and Harry have decided that once they are married they will move into rented accommodation again. The couple were spending £525 a month renting a home in the town but when the tenancy came up they decided to approach Harry's mum and ask if they could move in. Harry says it was a culture shock after almost four years away from the family home. As well as living with his mum, he works with her but he says she is "quite good at giving us our own space".

Maxine is thrilled to have all of her children back at home. "I love it," she says. "I think it's a great compliment that they wanted to come back – they could have found an alternative. I enjoy having them around the house."

She says she has not set any house rules. "I did all that when they were growing up. They know how to behave."

Despite her enthusiasm, Maxine admits there will be benefits when her children do leave home again: "I shall miss them but it will be nice to get some space back."