The Bank of Mum and Dad – the lender of last resort for their grown-up children unable to afford a deposit to buy a home – has moved into the private rentals market.

The country’s housing crisis has become so acute that parents are now having to subsidise their children’s rent to the tune of £1bn a year.

Research by the housing charity Shelter says that 450,000 adults need help from their parents to keep them in their rented home. An analysis of almost 4,000 adult people who rent carried out by YouGov suggests that more than one in 20 have either borrowed or received money from their parents this year to pay their rent or help them with moving costs.

Younger people are particularly reliant on their parents for help, with 11% of those aged 18-24, and 8% of those aged 25-34, receiving financial support. Shelter estimates that this amounts to about £850m a year on rent and £150m a year on moving costs.

“With housing costs sky high it’s not surprising that the Bank of Mum and Dad is no longer just relied on for help with buying a home, but renting costs too,” said Campbell Robb, Shelter’s chief executive. “We know that the majority of private renters are forking out huge proportions of their income to cover the rent each month, and that’s not even taking into account the extortionate deposits and fees that need to be paid.”

Almost 150,000 renting households in England were at risk of losing their home in the past year – some 350,000 people, says Shelter. “For those who aren’t lucky enough to receive help from parents, expensive and unstable private renting leaves many struggling,” Robb said. “We hear from people every day who simply can’t keep up with rising rents on where to live.”

Lou Hart has a 19-year-old son and a 13-year-old daughter. A specialist carer, she has been forced to move several times while renting flats in villages around the town of Guildford in Surrey.

“I had some housing issues from 2010 onwards and had to move around a lot – six times in a matter of five years,” she says. “Letting agents are fairly ruthless. The charges they put on are totally ridiculous a lot of the time. Each house move cost me between £2,000 and £3,000. Around here, a two-bedroom flat that is anywhere near reasonable was about £1,200 [a month] a few years ago; the prices are even higher now.”

In 2014, Hart, 45, moved in with her then boyfriend, but the relationship didn’t last. “After a few months of living on sofas I was not in a particularly good way and my dad helped me get a flat,” she says. “He’s helped me several times, either with rent or the deposit. ”

The problem is particularly serious in London, where Shelter claims 54% of private renters are struggling to pay. Government figures show rents rose by 19% in London in the past five years. And while the average for a two-bedroom flat in the capital is now more than £1,600 a month, wages have not kept pace.

An analysis of statistics from the Ministry of Justice suggests eviction hotspots are emerging in unlikely places. In Enfield in north London, one household in 23 faces eviction. Areas such as Luton, Thurrock in Essex and Peterborough are also giving cause for concern.

Research published on Saturday by the Resolution Foundation suggests that declining home ownership and rising private rents mean that today’s millennial generation will have spent £44,000 more on rent by the time they reach 30 than their baby-boomer parents.

Theresa May has spoken of the need to tackle rising housing costs. Robb said: “The new prime minister needs to give back hope to the millions of renters being left behind by our housing shortage, by quickly putting in place measures that will build homes that people on ordinary incomes can actually afford.”