WASHINGTON, June 8 (Reuters) - U.S. Housing and Urban Development Secretary Mel Martinez, adding to Bush administration questions regarding Fannie Mae and Freddie Mac, urged the mortgage-finance giants on Saturday to work harder to help low-income people and minorities buy homes.

The Bush administration has yet to describe its policy toward the shareholder-owned but congressionally chartered companies, known as government-sponsored enterprises or GSEs because of the benefits Congress grants them to help them promote home ownership.

But in the past two weeks, White House and Treasury officials have issued statements calling for tighter regulation of GSE financial disclosure and boards of directors and expressing concern that retail investors may mistakenly think GSE securities are guaranteed by the government.

Martinez said the GSEs may not have lived up to their congressionally mandated goal of outperforming the broader market in financing home loans for segments of the population that tend to be less likely to own their own homes.

"The government-sponsored enterprises, created to increase the liquidity of mortgage markets, are supposed to lead the market in reaching underserved populations. While these entities have increased their commitments, too often they are seen as lagging behind lenders," Martinez said in remarks prepared for delivery.

Fannie Mae spokesman Robert McCarson agreed that more needed to be done but said his firm was already a prominent provider of mortgage financing to U.S. minority homebuyers. "We are the largest private source of home financing in the United States, and we are the largest private provider of financing for minorities."

The company has a $2 trillion commitment aimed mostly at "increasing home ownership among minorities and other underserved populations," McCarson said. Freddie Mac could not be reached for comment.

The HUD secretary, speaking to the National Association of Home Builders, said the mortgage finance, real estate and home-building industries had profited from government policies supporting home ownership. He called on the private sector to do more to promote home ownership rates among low-income people and minorities, whose home ownership rates are lower than the broader population.

Low Incomes, Minority Neighborhoods

As part of their congressional charters, Fannie Mae and Freddie Mac must meet goals set by HUD for financing loans to home buyers who are low-income or live in neighborhoods with high concentrations of minority residents. The companies, which do not lend directly to home buyers but purchase mortgages from lenders and hold them or package them as securities, have met those goals.

But a recent HUD study concluded the two GSEs were not financing as high a percentage of single-family homes for low-income borrowers or in high-density minority areas as the broader market. The two companies disputed the report, saying it included data on high-interest rate, high-cost loans to borrowers with blemished credit histories that they had only recently begun to finance in limited quantities.

Both companies point to high volumes of financing for loans for minorities and programs aimed at making it easier for low-income people to buy homes as evidence of their efforts. Comments by the administration come as the Bush team sorts out its policy on the GSEs, which despite some vocal congressional and industry criticism, enjoy broad political support, including backers in the Congressional Black Caucus.

The mortgage finance companies have also been a key cog in the vibrant housing industry, which has buoyed the U.S. economy through its recent downturn.

Congressional hearings are expected this summer in the Republican-led House of Representatives on proposed legislation that would strip some of the companies' charter benefits in the name of post-Enron stricter financial disclosure.

The Democratic-led Senate, whose leaders have been supportive of Fannie Mae and Freddie Mac, appears unlikely to take up any similar legislation.