House prices are falling throughout the country, and a growing glut of homes, on top of a recessionary economy and tight credit, threatens to weaken them even further.

The slide in prices accelerated in February, according to the latest Standard & Poor's/Case-Shiller home price index.

The index for 20 housing markets fell 12.7 percent from a year ago and 2.6 percent from January. Its index of 10 metro markets slumped a record 13.6 percent from a year ago.

All 20 markets were down in February from January, and only Charlotte, North Carolina, was up (just 1.5 percent) from a year ago. Ten of the 20 had double-digit annual declines.

"There is no sign of a bottom in the numbers," said David Blitzer, chairman of the index committee at Standard & Poor's.

Prices will continued to be pressured as more homes come on the market through foreclosures.

RealtyTrac, an online real-estate-data company, reported that foreclosure filings more than doubled in the first quarter of 2008 from a year ago and rose 23 percent from the last three months of 2007.

"Foreclosure activity in the first quarter increased on a year-over-year basis in 46 out of the 50 states and in 90 of the nation's 100 largest metro areas, demonstrating that most regions of the country are seeing more foreclosures," said James Saccacio, chief executive of RealtyTrac.

Census Bureau data on Monday showed the number of vacant homes in the United States grew by one million, to a record 18.6 million.

"I don't think we're anywhere near a bottom in housing,'' Eli Broad, the co-founder of KB Home, told Bloomberg TV. "We're going to have a big inventory of unsold, unoccupied homes that's going to take three or four years to clear out.''