The National Commission on Neighborhoods, in a report that four of its 20 members refused to sign, yesterday urged Congress to outlaw the practice by some lending institutions of refusing to make mortgage loans in declining areas of cities.

The commission, which has been plagued by internal dissension, issued a 107-page summary of its 800-page final report after spending $1 million and 15 months studying why certain city neighborhoods are in trouble.

Among some 200 other recommendations, the commission called for increasing the amount of federal money spent on social services money directly to neighborhood organizations and denying mayors the power to veto neighborhood groups' proposals for federal money.

Three members of Congress who served on the commission -- Sen. Jake garn (R-Utah), Rep. James J. Blanchard (D-Mich.) and Rep. Joel Pritchard (R-Wash.) -- did not sign the report. Sen. William Proxmire (D-Wis.), the other congressional member, did sign, saying he supports the "major thrusts" but not the report's recommendations for increased federal outlays.

The fourth commission member who refused to sign the report is John McClaughry, president of the Institute for Liberty and Community of Concord, Vt.

Even one of the signers, Norman Krumholz, planning director of Cleveland, issued a stinging criticism of the report. He called it a "smorgasbord of major and minor issues," and said the recommendations, "which appear to include something for each participant's interest, fall far short of a coherent strategy to deal with the problems of our neighborhoods."

Krumholz said that "major issues like proverty, interracial conflict and segregation and institutional inequality receive insufficient attention, while the key issues of crime and schools barely surface at all."

McClaughry, Garn and Robert B. O'Brien Jr., president of the Carteret Savings and Loan Association of Newark, N.J. wrote, "We are frankly astonished by the commission's vote to reject a recommendation" for withholding federal community development block grant funds from suburbs that refuse to accept a fair share of lower-income housing.

Commission administrator John Eade said the majority felt the commission should deal with city problems "rather than arbitrarily castigate the suburbs."

In recommending a statutory ban on redlining, or discriminatory lending practices, the commission noted that such practices are forbidden only to savings and loan associations through a Federal Home Loan Bank Board regulation. It said a law is needed that would apply to banks, credit unions and all other lending institutions.

Gale Cincotta, a neighborhood leader from Chicago and head of the National Training and Information Center there, said the law should provide that violators would lose their board of directors seats and their institutions would lose their charters.

The commission also urged that various federal programs, including many of those of the Department of Housing and Urban Development, should be directed more to aiding lower income people.

It endorsed the idea of a "community full employment" strategy, which proposes that more federal and state programs should be developed to create jobs and raise the economic base of declining neighborhoods.

Asked whether he expected more support for the recommendations from Congress or the administration, commission chairman Joseph F. Timilty replied, "The administration."

He said Stuart E. Eizenstat, the president's chief domestic adviser, "liked the tenor and the self-determination aspect of the report and said he would look closely at its recommendations."

Asked about the dissenting opinions from several commissioners, Timilty said, "They're not dissents. They're additional views."