Fitch Ratings said it expected the value of property to fall by a further 17% from its current level, leaving prices 30% below their peak in October 2007.
A drop of this level would knock an additional £28,000 off the average price of a home, leaving it at £134,000 on the Nationwide measure.
The prediction comes the day after Halifax said house prices rose for the third month in a row during September, increasing by 1.6%. Nationwide also reported the fifth consecutive monthly price increase during the month, with property values rising by 0.9% to the same level they were at in September last year. But Fitch said the price rises seen during the past few months were a "temporary respite" and the downward trend would resume as unemployment continued to increase and mortgage availability remained tight.
Brian Coulton, head of global economics at Fitch Ratings, said: "The UK's average house-price-to-income ratio remains significantly higher than the long-term average. "A 30% fall from the peak of October 2007 would bring this ratio back in line with the long-term average.
"In comparison, the house price declines in the recession of the early 1990s saw the average house-price-to-income ratio fall below the long-term trend."
The group warned that unemployment, which it expects to peak next year and remain high into 2011, would weigh on house prices
