Nearly half a million households in the UK are still in negative equity.
New figures show that almost 500,000 homes are worth less than the mortgages on them, the BBC reported.
The problem is worst in areas of the country where houses prices have not yet recovered from the economic slump.
For example, in Northern Ireland 68,000 homeowners, or 41 per cent of borrowers, were in negative equity at the end of last year.
This compared to 16 per cent in north-east England and Cumbria. Six months previously the figure stood at 14 per cent.
In Scotland, 13 per cent of households were in negative equity.
The figures, released by the mortgage group HML, are based on data from more than one million home loans.
But in London, only 1 per cent of borrowers were in difficulties, following the increase in the capital’s property prices.
And overall, just 8 per cent, or 463,000, of mortgage holders were in negative equity – an improvement on five years previously.
Negative equity occurs when the current value of a property is less than the outstanding debt on a mortgage.
It creates a problem for the bank or the building society, because they no longer have enough security to cover the loan, and means that homeowners cannot sell the property without paying back the difference.
Kate Faulkner, of Propertychecklists.co.uk, told the BBC: "Negative equity is only a problem if you need to move.”
But she added that some lenders will consider transferring a mortgage to another property.
"It may well be that they will allow you to take the mortgage with you, and take that loan that you owe to the next property. So it's not disastrous if that happens. The trick is to talk to your lender as early as possible,” she said.
Renting out their property is often the only option for those trapped in negative equity.