British house prices fell 4.8 percent year-on-year in August, a survey by property Web site Rightmove showed on Monday, the fastest fall since the series began six years ago.
Rightmove said property prices fell by 2.3 percent, or 5,403 pounds ($10,120) on the month in August, bringing the average asking price down to 229,816.
For July, Rightmove reported a two percent year-on-year drop in house prices.
Figures are not seasonally adjusted, but add to overwhelming evidence of a severe downturn in the British housing market as buyers find it harder to get a mortgage as banks tighten lending conditions and the economy cools.
London saw the sharpest fall among regions last month, with average prices sliding by 5.3 percent after a 0.3 percent rise the previous month.
Prices in the capital were 3.8 percent down on a year ago.
"Sellers coming to the market in the middle of the summer holiday season tend to be more motivated. London in particular appears to be having its own special summer sale with over 21,000 pounds off in a month," said Miles Shipside, commercial director at Rightmove.
The survey also showed the seventh consecutive monthly rise of unsold houses on the books of estate agents to a record 78 properties on average in August, up from 77 in July.
Shipside said that the number of transactions expected to be completed this year was in danger of falling to its lowest level since 1959.
The number of new houses on the market also fell to 106,000 in August, a survey low, and 25 percent down on the number Rightmove would expect at this time of year.