Big-city neighborhoods are slowly becoming more integrated - but overall, every large US city still has high levels of housing segregation, according to a new analysis of 1980 census data.
Released Thursday by the Citizens' Commission on Civil Rights, a private group whose members include Cabinet officers from the Eisenhower, Johnson, and Nixon administrations, the report concludes that the average ''segregation index'' for 28 large cities in the United States declined from 87 in 1970 to 81 in 1980.
In a metropolis with a segregation index of 100, every residential block would be either all white or all black. An index of 0 would be awarded a city where the racial mix of every block reflected the racial mix of the city as a whole.
The report points out that some Southern cities have made much progress in housing integration. Dallas, Jacksonville, Fla., Houston, Nashville, Tenn., and Richmond, Va., all saw their segregation indexes decline 10 points or more during the 1970s.
The least segregated large US cities are Gary, Ind., and Oakland, Calif. The dubious distinction of ''most segregated'' goes to three major Midwest towns: Chicago, Cleveland, and St. Louis.
Overall, concludes the commission, segregation has persisted in US cities partly because the government has made only half-hearted attempts to eradicate the problem.
''We have not as a nation demonstrated that we have the commitment to take our fair-housing laws and implement them in a meaningful way,'' charges Arthur S. Flemming, secretary of Health, Education, and Welfare under President Eisenhower and a Citizens' Commission member.
For instance, as yet no government regulations have been issued to fully implement one major fair-housing law, Title VIII of the 1968 Civil Rights Act - though the law itself was passed 15 years ago. The Carter administration, in its waning days, issued a preliminary set of such regulations. The Reagan administration withdrew the proposed rules before they became final.
At about the same time, points out the commission's report, a Senate filibuster killed a bill that would have given the fair-housing law more enforcement teeth, and extended its protection to the handicapped.
The commission also charges that the Justice Department, under President Reagan, has sharply cut the number of fair-housing cases filed: only five such suits have been filed during the last two years, compared to an average of 32 per year under previous administrations.
The Justice Department has filed, however, a wide-ranging case against the town of Cicero, Ill., charging that the Chicago suburb discriminates against blacks in both housing and jobs.
To improve US fair-housing laws, the Citizens' Commission recommends:
* Legislation to establish a federal procedure to help individuals who feel they've been discriminated against when looking for housing. Currently, individuals have to file a private lawsuit if they feel they're victims of segregation.
* Extension of the fair-housing law to cover the handicapped and families with children.
* Establishment of a private sector task force to further study weaknesses in federal fair housing laws.