TAMPA - Home prices tumbled in the Tampa Bay area in April, a slide that has continued for months and mirrors a national trend.

Home prices in the Tampa area plummeted 20.4 percent in April compared with the same month last year, the Standard & Poor's/Case-Shiller home price index showed. Prices have plunged 25 percent in the area since the housing boom's peak in July 2006, according to the survey.

In a month-to-month comparison, the area's home prices dropped 2.1 percent in April after a 3.4 percent decline in March, the index showed.

"If there is anywhere to look for possible improvement, it would be that the pace of monthly declines has slowed down for most of the markets," said David Blitzer, chairman of the index committee at S&P.

For the first time, all 20 cities tracked by the index posted an annual decline in home prices.

Of the 20 cities, six recorded steeper price decreases than Tampa.

In Miami, April home prices were down 26.7 percent, compared with April 2007. Las Vegas posted the largest annual decrease, 26.8 percent. Charlotte, N.C., showed a decline for the first time, albeit the smallest decrease: less than 1 percent.

Rising borrowing costs aren't helping, Blitzer said. Last week, Fannie Mae, the largest mortgage buyer, cut its forecast for new and existing home sales this year as rates on 30-year fixed mortgages jumped to an eight-month high of 6.42 percent.

"If you go back a couple of years, mortgages were easy to find," Blitzer said. "Now the banks have all locked the door."

Overall, the S&P/Case-Schiller index is down 15.3 percent from a year ago. The gauge, which uses available sales data, has fallen every month since January.

Blitzer expects home prices to keep falling, citing a surplus of homes, an ailing economy and record-high gasoline prices. What's more, consumer confidence is at a 16-year low, he said.

"Both in Tampa and nationally, the trend will continue for quite a while," Blitzer said. "One hint of better things is that eight of the cities saw home price gains" in April, he said.

The month-over-month gains were led by Cleveland and Dallas.

Two more housing sales reports are expected this week. A Commerce Department report on new home sales is expected today. The National Association of Realtors is expected to release figures Thursday on existing home sales.

Information from Bloomberg News was used in this report. Reporter Russell Ray can be reached at  (813) 259-7870  or rray@tampatrib.com.