Single-family home prices dropped into double-dip territory in March as the housing market remained bogged down by inventory and weak demand, a closely watched survey said on Tuesday.

The S&P/Case Shiller composite index of 20 metropolitan areas declined 0.2 percent in March from February on a seasonally adjusted basis, in line with economists' expectations.

The price index was below the low seen in April 2009 during the financial crisis. The glut of houses for sale, foreclosures, tight credit and weak demand have kept the housing market on the ropes even as other areas of the economy start to recover.

The 20-city composite index was at 138.16, falling below the 2009 low of 139.26.

This month's report is marked by the confirmation of a double-dip in home prices across much of the nation, David Blitzer, chairman of the index committee at S&P Indices, said in a statement. Home prices continue on their downward spiral with no relief in sight.

Prices in the 20 cities fell 3.6 percent year over year, topping expectations for a decline of 3.3 percent.

In the first quarter, the national index fell 1.9 percent on a seasonally adjusted basis, compared to a decline of 1.8 percent in the previous quarter. On a non-adjusted basis, they fell by 4.2 percent in the quarter.

(Reporting by Leah Schnurr, Editing by Chizu Nomiyama)

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