Rising rents have prompted a record 12,000 tenants who are struggling with arrears to contact a debt advice charity this year.
The Money Advice Trust (MAT) said the number of calls it had dealt with about rental arrears between January and August was the biggest in the 26-year history of its National Debtline and around double the number it received during the same period in 2007.
The share of its clients who have fallen back with their rent is also increasing, and stands at nearly one in 10, compared with 8% last year and 6% five years ago.
For the first time, people who rent their home now account for more than half of the total calls that the National Debtline receives, meaning tenants are also becoming mired in a broader range of debt problems, MAT said.
The charity warned of a "dangerous spiral", with tenants sinking further into debt as increased demand in the sector pushes their rents up even higher.
The rental sector has become overheated as people struggle to get on the property ladder, either because they cannot raise the 20% deposit often demanded by lenders or meet their toughened borrowing criteria.
A report by the Yorkshire Building Society found that would-be first-time buyers face spending more than eight years saving for a typical deposit of £26,000. As more people remain in the rental market for longer, the increase in demand means that rents are pushed up further and tenants face an even tougher time meeting their payments.
Rents rose for five months in a row to reach a new high in August of £734 on average a month, according to a recent study by LSL Property Services, which owns chains Your Move and Reeds Rains.
A Department for Communities and Local Government spokesman said: "Ministers are determined to back this country's private rented sector, which provides homes for millions of people. That is why as part of the housing and growth package announced last month the Prime Minister confirmed a new £10 billion Government guarantee to encourage more developers into the market, and plans to build an additional 5,000 homes specifically for private rent.
"But another important measure the Government is doing is stopping the imposition of excessive red tape on private landlords, which would have pushed up rents and reduced choice for tenants. Statistics actually show that rents have fallen in real terms, although there are local variations."