Half the population is worried about mortgage rates, and a quarter (26%) of people with mortgages fear having their home repossessed, according to a new study.
The findings, published in the Which? Quarterly Consumer Report, reveal an increasing gap between older, more financially secure homeowners and many people aged 30-49 who bought their homes recently.
A large amount of people in the latter category are so-called "mortgage prisoners", trapped in their current mortgage deal and unable to switch when rates increase.
The report also revealed that home ownership is increasingly out of reach for first-time buyers as rising rents make it harder for people to save for large deposits.
More than half (54%) of people under 30 who do not own a home are worried about getting on the property ladder.
Lenders have also increased mortgage arrangement fees, which rose by around 60% in 18 months to an average of £1,472 in August.
The findings come as banks and building societies are being given access to cheap funds through the Government's Funding for Lending Scheme.
Which? is calling for the Government to ensure lenders benefiting from the scheme set lower borrowing costs to help everyone, not just those with significant equity.
Richard Lloyd, Which? executive director, said: "The housing market is failing not just one but two generations of consumers, with many mortgage prisoners trapped on their current deal and young people excluded from the housing market altogether.
"The Chancellor must put tougher obligations on banks that get cheap finance through the Government's Funding for Lending Scheme so that more is done to help those who are struggling through no fault of their own, and especially to ensure that mortgage prisoners and first time buyers can benefit from lower borrowing costs."
