One in five mortgage holders is worried about meeting their repayments in the next 12 months, according to the Financial Services Authority (FSA).
The housing market has slowed since last summer
And a quarter of those do not have any plans for dealing with the issue, the poll for the financial regulator found.
The survey was small, with just 573 people with a mortgage giving answers.
But the FSA is sufficiently concerned about the situation that it is launching a £2m advertising campaign and an advice guide for homeowners.
The FSA is concentrating its campaign on householders whose fixed-rate deals are coming to an end this year.
"Economic conditions are getting tougher, putting pressure on family finances," said Chris Pond, FSA director of financial capability.
The poll of 2,011 people aged over 16, of whom 573 were mortgage holders, found that 19% of those asked were concerned about meeting the cost of their mortgage repayments.
Last month, the Council of Mortgage Lenders (CML) said repossessions rose by 21% in 2007 to 27,100 homes, the highest figure since 1999.
It also said the numbers of mortgages behind on payments rose by 8.6% compared with 2006.
The CML expects the number of homes taken over by lenders to rise further in 2008, as the credit squeeze continues to tighten.
Meanwhile, a separate study, by the Centre for Economics and Business Research for Asda, suggested that families were £5 a week worse off this January compared with a year ago because of rising petrol and food costs.
The FSA has published a new guide to help people manage their mortgage in preparation for some difficult times.
The checklist suggests that people check their budgets and think about how they would cope if their mortgage payments increased significantly.
It also advises that homeowners start looking at their options well in advance of their current deal coming to a close.
For those already seriously struggling, it says that they should not panic but should talk to their lender and seek free, confidential advice from an independent debt advice agency.