A coalition of legal groups has filed an unusual class-action complaint with the U.S. Department of Agriculture (USDA), charging that discriminatory policies of its Farmers Home Administration (FmHA) have speeded the exodus of blacks, women, Indians and the elderly from farming in North Carolina.

The complaint, drawn up by the North Carolina Association of Black Lawyers and other advocacy organizations, called for an investigation of FmHA procedures that it argues have prevented hundreds of minority farmers from continuing in business by illegally denying loans for land purchases and annual operating expenses.

According to the complaint, black-farmer participation in the main FmHA loan programs fell from 5.4 percent in 1980 to 1.5 percent in 1986, while Indian participation dropped from 4.1 percent to one percent during the same period.

"The impact of FmHA's discriminatory practices has been devastating on class members in North Carolina," the complaint said. "In the {20} counties referenced in this complaint alone, these two groups comprise over 41 percent of the total population."

"FmHA's actions have further resulted in a disproportionate number of class members being driven out of farming. Between 1978 and 1982, the total number of black and Indian farmers declined 23.2 percent, compared to 9.8 percent for the white farmers. Additionally, the total number of female farmers declined 15.7 percent."

Although reliable figures are not maintained by the government, North Carolina, with approximately 5,300 black farmers -- about one-tenth of the national total -- is regarded as the largest black-farmer state after Mississippi.

Departmental sources said the complaint was unusual for its breadth and for an additional wrinkle, which charged that FmHA's alleged practices violated the federal Equal Credit Opportunity Act, which bars discrimination by creditors.

The lawyers' group called for a joint investigation by USDA and the Federal Trade Commission in connection with its charges of credit-law violations and urged the department to revamp FmHA regulations to require a freer flow of agency farm-loan funds to minority farmers in North Carolina.

USDA has made no official comment on the sweeping complaint. Sources said the department has consulted with the FTC, but has made no decision about a joint investigation. Department legal advisers also have been asked to decide whether the complaint is a legitimate class-action procedure.

The FmHA, considered the government's last-resort lender for farmers who cannot get credit elsewhere, has been criticized for years by private and public civil rights groups over lending policies that they contend discriminate against blacks and hasten their demise in farming.

The U.S. Commission on Civil Rights, reporting in 1982 on the decline of the black-farmer population, charged that a failure of FmHA to provide adequate financial aid had "hindered the efforts of black farmers to remain a viable force in agriculture."