The nation’s home prices have fallen to their lowest level since 2002, according to a private report, casting a troubling shadow over what has otherwise been a brightening economic recovery.

Although analysts have been nervously eyeing rising oil prices and Europe’s struggling economy, Tuesday’s S&P/Case-Shiller index of property values report offered a sobering reminder that the still-shaky housing market remains one of the most potent threats to a robust recovery.

In December, the index fell 4 percent from a year earlier, after decreasing 3.9 percent in November. The decline was reported one day after another measure showed an encouraging increase in the number of people signing contracts to buy previously owned homes.

The continued trouble in the housing market has proved to be among the most vexing problems in the economic downturn. Even as the stock market has reached a four-year high, the unemployment rate has declined sharply and consumer confidence has perked up, housing remains problematic, putting a damper on economic growth.

“It is hard to get entirely enthusiastic about the recovery when housing prices are still falling,” said Mark Zandi, chief economist at Moody’s Analytics.

In the Washington area, which had remained one of the strongest markets during the housing crisis, the home price index fell 1.2 percent in the fourth quarter of 2011, compared with the third quarter 2011. But other data show that the housing market in the area had recovered in January, said John McClain, a senior fellow at George Mason University’s Center for Regional Analysis.

Actions taken by the Obama administration to bolster the housing market have only helped on the margins. A tax credit for first-time home buyers helped prop up housing sales and prices, but they both tumbled once the incentive expired, hurting some new homeowners, analysts point out. In addition, the administration’s incentives for banks to aid homeowners who owe more on their loans than their houses are worth have helped far fewer people than expected.

GOP presidential candidates, meanwhile, have mostly stayed away from offering any housing policy prescriptions other than to let the market hit bottom and recover on its own.

A Senate Banking Committee hearing Tuesday focused on the state of the nation’s housing, lawmakers and federal regulators traded jabs over the other’s inability to more effectively tackle the persistent problem.

Some Republicans have criticized the Federal Reserve for wading into political waters after the agency last month released a report that suggested additional federal effort to aid troubled homeowners — even at taxpayer expense — could be helpful to the broader economy.

Federal Reserve governor Elizabeth Duke told lawmakers that in a typical economic cycle the housing market would decline, bottom out and then pick back up as the economy begins to improve and demand increases. But this time has proven different.

“Six years after aggregate house prices first began to decline, and more than two years after the start of the economic recovery, the housing market remains a significant drag on the U.S. economy,” Duke said in prepared remarks. She added: “The current recovery has not followed this script, in part because the problems in the housing market are a cause of the downturn as well as a consequence of it.

Analysts called the decline in Case-Shiller index evidence of the glut of distressed properties that remained unsold, depressing prices even as borrowing costs have declined to near historic lows. Zandi said that 3.6 million first mortgages — more than 7 percent — were at least 90 days late, and most likely headed toward foreclosure.

“I think we still have some way to go down," said Dean Baker, co-director of the Center for Economic and Policy Research. “The problem is we still have enormous oversupply.”

With prices down, people are thinking twice about buying homes, especially if they know they will be moving in a few years.

“Owning a home is not necessarily the best move for everyone,” said Mark H. Goldman, a mortgage broker and lecturer at San Diego State University. “As a nation, we are rethinking the whole notion of home ownership.”

The Case-Shiller home price index showed that prices dropped between November and December in 18 of the 20 metropolitan areas that are followed. Together, the 20 markets covered by the index account for about half of the nation’s housing. The steepest declines were in Atlanta, Chicago and Detroit. Miami and Phoenix were the only cities to show an increase.

Overall, prices fell in 19 of the 20 cities in December compared with the same month in 2010. Only Detroit posted a year-over-year increase. Prices in Atlanta, Las Vegas, Seattle and Tampa dropped to their lowest points since the housing crisis began.

At a national conference of home builders earlier this month in Florida, Federal Reserve Chairman Ben Bernanke said that housing could either fuel a strong economic resurgence or slow it to a crawl.

“The economic recovery has been disappointing in part because U.S. housing markets remain out of balance,” he said. “For these reasons, and because the troubled housing market depresses construction activity and employment, we need to continue to develop and implement policies that will help the housing sector get back on its feet.”