A Washington-based interest group that publicly favors Nicaragua's counterrevolutionary rebels has channeled U.S. government funds to aid Nicaragua's principal human rights commission, according to officials of the U.S. organizations involved.

The National Endowment for Democracy, a public foundation that disburses U.S. government funds, made a $50,000 grant for 1986 to assist in the translation and distribution outside Nicaragua of the Permanent Human Rights Commission's monthly report. The commission is the only nongovernment organization in Nicaragua regularly monitoring rights violations by the leftist Sandinista government.

The grant was administered by Prodemca, a small tax-exempt group that focuses on Central American issues. During Congress' March debate for a $100 million aid package for the rebels, Prodemca ran large ads in The Washington Post and The New York Times calling for military aid for the contras, as the rebels are called.

Backing from an openly pro-contra U.S. organization could be seen to compromise the commission's political independence and expose the commission to being attacked or closed down by the Sandinista government as it prepares for all-out war with the contras.

None of the funds for the commission's work were paid within Nicaragua, said officials of Prodemca, the endowment and the commission.

The endowment was created in 1983 to "strengthen democratic institutions throughout the world through private, nongovernmental efforts," according to its "Statement of Principles and Objectives."

It gives grants to foundations that have been set up by the Democratic and Republican parties, the Chamber of Commerce and the AFL-CIO. The endowment also gives funds for dispensing abroad to independent conduits such as Prodemca.

Leading U.S. human rights activists have questioned the wisdom of the commission's accepting any help from Prodemca at a time when the confrontation between the Reagan administration and the Sandinista government is sharply polarizing Nicaraguan politics.

Aryeh Neier, vice chairman of Americas Watch, the principal independent U.S. committee monitoring rights in Latin America, said, "It is a great mistake for the commission to accept that kind of funding."

Since June 25, when the House of Representatives approved $100 million in contra aid, the Sandinista government has taken sudden, harsh measures against those it accused of being Reagan administration "paid agents." It closed La Prensa, the only opposition daily newspaper, for an indefinite period on June 26.

At a press conference several days after the House's aid approval, high-ranking Sandinista Commander Bayardo Arce cited grants made by Prodemca to La Prensa as "the reason we closed it." Since 1985 Prodemca channeled two grants totaling $150,000 from the endowment to La Prensa. The paper had long been a critic of the government.

When the government expelled Nicaraguan Roman Catholic Bishop Pablo Antonio Vega to Honduras July 4, it said one of its motives was his participation in early June in a Prodemca conference in Washington.

Prodemca director Penn Kemble said in a telephone interview from Washington last week that he was aware his group's sponsorship could create problems for endowment grant recipients in Nicaragua after it made public statements backing the contras.

Soon after Prodemca decided to go public with its position, Kemble consulted with endowment directors to find out "how we could be relieved" of $50,000 remaining of a second grant for La Prensa. In May the money reverted to the endowment, Kemble said. This information apparently did not reach the Sandinista government before it shut down the paper.

However, Prodemca continued its support for the commission. Kemble said the $50,000 grant -- down from $169,000 in an original 1985 Prodemca proposal -- went to "individuals suggested by the commission" in San Jose, Costa Rica, to translate the commission's monthly report into five languages and distribute 6,000 issues overseas.

The funding began in January 1986. Kemble said Prodemca settled on paying the grant in Costa Rica instead of directly to the commission after the Sandinista government suspended many civil liberties in a state of emergency declared last Oct. 15.

A spokesman for the endowment, Mark Plattner, said Prodemca is paid $6,000 from the grant for its administrative costs.

"We of course have taken a stand on the contra issue," Kemble said. But he added: "Whatever funds went for any groups in Nicaragua were transferred under careful contract guidelines, and none were expended inside Nicaragua for anything that could be construed as antigovernment activities. In no way could this be associated with the armed opposition."

The commission's director, Nicaraguan lawyer Lino Hernandez, said in an interview here, "Our institution is not receiving one single cent" from Prodemca or the endowment. He said the people in Costa Rica who translate the report are "foreign to our commission."

Hernandez said he did not know the names of the persons doing the translations. He denied having discussed the project directly with Prodemca. "We have no agreement with them," he said.

But he said the commission "looks favorably" on the overseas distribution of its reports.

The commission, with 26 employes, is housed in a ramshackle Managua office spattered with graffiti painted in past years by Sandinista sympathizers. The commission centralizes, in relatively precise records, reports about arbitrary capture and other government abuses against Nicaraguans who do not support the ruling Sandinista party.

The commission has been criticized by international human rights watchdog institutions, including Americas Watch, for failing to investigate abuses by contra guerrillas.

The commission stopped distributing its 10-page monthly report in Nicaragua for four months in December 1985, after the government imposed prior censorship on it. Since April the commission circulated 500 copies each month, Hernandez said, even though the censorship had not been formally lifted.

The Nicaraguan government runs a separate human rights commission that defends Sandinista policies and does not regularly report cases of alleged government abuses.

In 1985 Prodemca also received $150,000 from the Endowment for Democracy for an organization called the Nicaraguan Center for Democratic Studies. The center was to be "a private nonpartisan entity" in Managua for training and research on "freedom of the press, property rights, private enterprise, . . . political and civil rights and the rule of law," according to Prodemca's 1985 proposal.

The center would "develop proposals or steps our governments and societies should take to implement the promises of the anti-Somoza revolution," the proposal stated, in a reference to the 1979 overthrow of the late ruler, Anastasio Somoza Debayle.

The center's board was to include prominent leaders of the main opposition political parties grouped in the Nicaraguan Democratic Coordinating Group. However, Prodemca head Kemble said the center never came into existence. It was to be formed for the purposes of the grant.

Staff writer Sidney Blumenthal in Washington contributed to this report.