U.K. house prices rose sharply in January after a surprise decline in December, lender Halifax said Thursday. According to the Halifax house price index released by HBOS PLC , house prices rose 1.3% on the month in January and were 9.9% higher on the year. In December, Halifax said prices fell 1.0% on the month and were 10.5% higher in annual terms. The rise in house prices during December was stronger than expected. Economists surveyed by Dow Jones Newswires last week estimated prices rose 0.8% on the month and 9.6% on the year. Despite the monthly gain, however, Halifax said that the steep monthly fluctuations are in line with a slowing housing market. "The mixed pattern of monthly price rises and falls in December and January is consistent with a slowing market," said Martin Ellis, Halifax's chief economist. The average U.K. house price was GBP188,623 in January, up from GBP186,035 in December, Halifax said.