Although women have generally found it easier to obtain mortgage loans since passage of the equal credit laws in the mid-1970s, lenders continued to discriminate against racial and ethnic minorities, a recent study for the Department of Housing and Urban Development shows.

The survey of lending patterns in the nation's two most populous states -- New York and California -- revealed that in at least half the areas surveyed, black applicants were denied credit much more often than whites. And in California, the report said, Hispanics were "consistently discriminated against" by state creditors.

The report, prepared for HUD by the Joint Center for Urban Studies of Massachusetts Institute of Technology and Harvard University, backs up the views of supporters of the proposed Fair Housing Act. The bill, which would toughen enforcement of existing housing law, was passed by the House Thursday.

Current law prohibits housing discrimination based on race, color, sex, national origin or religion. The new law would extend the protection to the handicapped.

But more important to those denied housing credit, the law would ban certain real estate practices such as redlining, used by some creditors to deny loans to potential home buyers in inner-city areas.

To enforce the new law, HUD would be allowed either to file housing discrimination complaints with an administrative law judge or to refer cases to the Justice Department for possible prosecution in the courts.

The immediate impact the new enforcement powers would have is unclear, however. Since the 1974 Equal Credit Opportunity Act banned discrimination on the basis of race, sex, marital status or location of property went into effect, the Justice Department has brought less than 100 suits for alleged violations.

Practices considered discriminatory under the 1974 Equal Credit Opportunity Act and the Fair Housing Act include denial of an application, charging about-average interest, giving a smaller loan than originally sought, variations in loan fees and underappraising the property.

HUD initiated its recent housing market study in New York and California to see if the laws were working, Among the findings:

Blacks in many areas of the two states were discriminated against significantly more than whites.

California Hispanics were consistently discriminated against, but Hispanics in New York generally were treated the same as whites.

Male-only households in New York were more than twice as likely to be denied mortgages as a male-female household. In California, males were found to pay higher interest rates and loan fees.

While women were not victims of lender discrminiation, "a few study areas showed higher chances of application denial or downward modification for female-only applicants," the report noted. "The underappraisal of properties was the practice most often encountered by females. There was little evidence suggesting that lenders discount a wife's income."

The study was done in connection with a 1977 HUD program designed to "help remove the barriers that impede the full participation of women in the mortgage and homeownership market."

In the Washington area, the barriers seem to have fallen quickly: The number of single, female homeowners living alone jumped by 70 percent between 1970 and 1977, according to the Census bureau. A 45 percent increase in the number of two-or-more-person households headed by women was also noted.

Another part of the HUD program aimed particularly at "displaced homemakers," is a series of workshops being held around the country to educate women about their basic credit rights. Feminist groups such as the Women's Legal Defense Fund, the National Organization for Women and the League of Women Voters concur with the Justice Department and the Federal Trade Commission that since passage of the equal credit laws, there no longer are many cases of overt discrimination against woman in mortgage credit resulting in lawsuits and damages.

Women's groups maintain that, despite the laws, there still are a number of instances of subtle discrimination against female loan applicants. Most of these are settled satisfactorily, said attorney Janice Siegel of the Women's Legal Defense Fund, when reluctant lenders are "reminded" of women's credit rights.

Like the feminist groups and the regulators, HUD seems willing to admit that its survey may not have picked up subtle discrimination. "It is important to remember," the report stated, "the limitations of this study. Not reflected in the data, for example, are the number of prospective purchasers who may have been discouraged from even applying for a loan."

For instance, Shirley L. Birkhimer, a 43-year-old legal secretary separated from her husband, was raising her three teen-age children with the help of alimony and child support when she tried to buy a condominium in Fairlington Village five years ago.

Birkhimer subsequently charged in a lawsuit that she was turned down after the sales agent refused to count the suport payments as part of her income, despite the fact that she had been receiving them regularly for five years. The suit was filed against the Fairlington developer, CBI Fairmac Corp., and the lender, Royal Oak Mortgage Co.

With the support included, Birkhimer had an annual income of $18,000 and qualified for a $45,900 loan. Without it, she didn't.

After being refused the loan, she bought a condominium in Falls Church for $53,000, and brought suit against Fairlington to recover the difference in price between the two condos plus damages. The case was settled out of court and $5,000 was awarded to Birkhimer.

Between five and 10 of the suits brought by Justice involved mortgage credit, and a few of them, such as the one involving Birkhimer, dealt with sex or marital status, according to Walter Gorman of the department. An attorney general's report to Congress mentions a similar number of private lawsuits.

In one suit, United States vs. Citizens Mortgage Company, a Virginia development was charged in 1978 with discrimination on the basis of sex and marital status. A similar suit was filed in Kentucky against Citizens Bank and Trust Co. In both cases the lenders consented not to violate the law again.

In Markham vs. Colonial Mortgage Service Co. Associates, an Illinois savings and loan was charged with discriminating on the basis of marital status when it refused to consider the incomes ot two unmarried joint applications, but regularly did so for similarly situated married applicants.

A case of alleged discrimination in this area involved Marilyn Seiber, 35, of McLean. At the time she tried to buy a condo in Arlington in 1978, she was making $28,900 a year -- and had a doctorate in economics, 12 years of government service and no debts or dependents.

Seiber said she was told by the Continental Illinois National Bank of Chicago that because her utilities and condo maintenance charges -- added to the mortgage, taxes and insurance payments -- came to 34 percent of her income, she would need a co-signer on the loan. Seiber contends that the condo fees and utilities should not have been included, in which case her debt to income ration would have been only 27 to 28 percent.

Her father co-signed the loan. Only later did she learn her father was listed on the deed as co-owner, meaning that she could not sell the apartment without his signature. When she asked the bank to change the deed, the bank replied it was policy to require a co-signer if the debt ration is over 25 percent.

Seiber has taken her case to federal financial regulators to ask them to ascertain whether Continental requires everyone with a debt ration over 25 percent to have a co-signer and whether the bank requires every co-signer to be listed as co-owner.

Another gap in the HUD study was alleged by Zina Green, a fair housing consultant and a former employe of the Office of the Comptroller of the Currency. She contended the report was faulty because it does not compare three crucial underwriting criteria: the ratio of loang to value, the ratio of monthly payment to income and the ratio of total monthly debt service to income.

Had the authors looked at these ratios for loan applicants of both sexes with the same incomes, they would have uncovered some discrimination against women, Greene maintained.

For example, she said, men tend to have higher debt service ratios -- such as expensive sports car payments.

So if male experience in getting a mortgage loan is only compared to typical women on the basis of income and found to be equal, that in reality is a form of discrimination -- because women have a lower debt ration and are theoretically more creditworthy, she said.