The chairman of the U.S. Civil Rights Commission has accused Agriculture Secretary John R. Block and the Department of Agriculture of scuttling civil rights enforcement programs and intensifying discrimination against black farmers.

Chairman Clarence M. Pendleton Jr., speaking for the commission in a harsh letter to Block last month, said that developments during the last year indicate that equal rights conditions, "rather than improving, actually have worsened" at the USDA.

Pendleton said these developments "lead us to the conclusion that the department has dismantled, in 1982, the few civil rights enforcement mechanisms developed by USDA over the past decade . . . . We strongly urge you to reconsider the direction your department has taken in civil rights."

Block acknowledged Pendleton's letter in a brief response several weeks ago, saying that a more detailed reaction would follow.

In his four-page critique of the USDA, Pendleton emphasized:

Farmers Home Administration (FmHA) farm loans to blacks have "declined steadily" during the past year, while the agency has done nothing to alter inequities in the lending program cited by the commission a year ago.

While FmHA's personnel was increasing 5 percent, minority employment at the agency was falling to a level "well below the federal government's average rate of minority employment."

Civil rights enforcement at the USDA has come "to a virtual standstill." He noted the discontinuance of civil rights complaint investigations and the USDA's refusal to comply with civil rights enforcement requirements.

Although blaming Block for the overall situation, Pendleton blamed much of the department's laxness on civil rights on Isidoro Rodriguez, who was fired in February after nearly a year as head of the USDA's Office of Minority Affairs.

Rodriguez, a political appointee, was dismissed after press reports about a memo he sent to Block that proposed a wholesale change in civil rights enforcement at the USDA and suggested that the department take the lead in the Reagan administration in diluting equal-opportunity vigilance.

The Civil Rights Commission chairman's blast at Block and the department is the latest round in a three-way skirmish between the commission, the USDA and the House Agriculture Committee, which has pressured Block to put more emphasis on loans to minority farmers.

The commission reported in February, 1982, that the number of black-operated farms was declining at a faster rate than white-operated farms, and charged that FmHA discriminatory credit policies were hastening the demise of black farmers.

Block did not answer the commission's charges formally until August. His eventual response apparently was prompted by a terse inquiry from Rep. Ed Jones (D-Tenn.), chairman of the House Agriculture subcommittee on conservation, credit and rural development.

Block, responding first to Jones and then to Pendleton, contended that the USDA was improving its enforcement programs and rejected the allegation that FmHA policy was putting black farmers out of business.

But the secretary's assurances did not satisfy Agriculture Committee members, who in the report of a recently passed emergency credit and FmHA reauthorization bill expressed "dismay" and "concern" at FmHA's "little desire" to provide special limited-resource loan money to black farmers.

Rep. Thomas A. Daschle (D-S.D.) and four other committee members added supplemental views to the report on the bill, urging the USDA to "improve drastically and immediately its enforcement of civil rights laws and its attitudes toward them."

Since Rodriguez' firing, the Office of Minority Affairs has been headed by Cleo Spartin, on temporary assignment from the Office of Personnel Management.

Spartin said that the USDA's civil rights programs "do not show signs of being well-managed . . . . My impression is that this deterioration has occurred over the last eight or nine years."

She said that USDA officials are "totally supportive" of her efforts to upgrade the department's enforcement programs, and that Pendleton's allegations will be responded to "as forthrightly and directly as possible."