U.S. home prices dropped at the sharpest rate in two decades during the first quarter, a closely watched index showed Tuesday, a somber indication that the housing slump continues to deepen.

Standard & Poor's/Case-Shiller said its national home price index fell 14.1 percent in the first quarter compared with a year earlier, the lowest since its inception in 1988. The quarterly index covers all nine U.S. Census divisions.

Prices nationwide are at levels not seen since the third quarter of 2004, according to Maureen Maitland, a S&P vice president. However, the index is still up 60 percent versus 2000.

The narrower indices also set record declines in the first quarter. The 20-city index tumbled 14.4 percent, the lowest since that index was started in 2001. The 10-city index plunged 15.3 percent, a record in its 20-year history.

"There are very few silver linings that one can see in the data. Most of the nation appears to remain on a downward path," said David Blitzer, chairman of S&P's index committee.