The U.S.-backed Nicaraguan rebel movement expelled today one of its top leaders who had accused the CIA publicly of duplicity toward Congress and the anti-Sandinista insurgents.

Adolfo Calero, president of the Nicaraguan Democratic Force, said the group's National Directorate sent Edgar Chamorro a letter informing him of his dismissal because he had become what Calero called "a loose cannon." Chamorro confirmed that he had received the one-sentence notice in today's mail and said he thought that he had been fired at the behest of the CIA.

Chamorro's removal from the seven-member directorate sealed an estrangement that began last spring after younger officers took over the Honduran armed forces and ordered increased discretion for CIA-directed rebel activities in Honduras. Chamorro, who was spokesman for the rebels in Honduras, drew opposition from Honduran officers and CIA advisers because of his often frank descriptions of insurgent actions. Because of pressure from the Hondurans, Chamorro said, he was sent home and cut out of insurgent deliberations here and in Tegucigalpa, the Honduran capital.

The split broke into the open last month with Chamorro's revelations about a CIA manual advising rebels to "neutralize" certain Nicaraguan government officials and his charges that CIA officials who helped organize the main insurgent group here two years ago committed the Reagan administration to aid in overthrowing the Sandinista government.

The statements attracted wide attention because the word "neutralize" was taken as a euphemism for assassination, which is forbidden by presidential directive, and because Congress has barred the agency from spending funds for the purpose of overthrowing the Sandinistas.

In addition, Chamorro said CIA officials coached rebel leaders on how to make a good impression with congressional opponents and avoid raising delicate issues. The American Civil Liberties Union has filed suit charging that this could violate U.S. statutes barring the agency from seeking to influence other government bodies.

"That's ridiculous," Calero retorted in an interview. "If we were from the hills of Tennessee, maybe we would need it. But we are from a sophisticated country."

[CIA spokeswoman Patti Volz said she would not comment on Chamorro's charges about the agency's role in organizing and assisting the rebels. With respect to the charge that CIA officials helped rebel leaders present their case to Congress, she said, "We are in compliance with U.S. law and with our obligations and responsibilities to report to Congress."]

Chamorro, who lives in Key Biscayne, Fla., said that what he described as CIA duplicity about the insurgents' goals and activities was a large factor in his decision to speak out.

While the Reagan administration was telling Congress and the public that the United States was funding the rebels to interdict arms shipments from Nicaragua to Salvadoran guerrillas, Chamorro charged, CIA officials were telling the rebels privately that the real goal was to topple the Sandinista leadership. Then, he went on, the agency never provided the support necessary to reach that goal.

Calero, former owner of the Coca-Cola bottling plant in Managua, said today he and other leaders of the Nicaraguan Democratic Force -- FDN by its Spanish initials -- understood from the beginning that U.S. aid by law has been directed at stopping Nicaragua's support for Salvadoran guerrillas.

Chamorro also said the collegial FDN leadership changed during the past year until only three persons, working directly with the CIA, were making decisions. These three included Calero; Col. Enrique Bermudez, the FDN military commander and a directorate member, and Aristides Sanchez, Calero's personal assistant.

Bermudez and Sanchez were key figures in earlier rebel groups associated with followers of the late Anastasio Somoza, overthrown by the Sandinistas in 1979. The FDN was formed late in 1982, at CIA urging, to rid the struggle of its Somoza links to enhance its image in Congress and Latin America.

Rebel leaders said CIA funding ran out last June after Congress refused to appropriate more money pending reconsideration of the issue in February. But Calero has estimated that the FDN, still the largest and most active of several rebel groups, has kept going by raising slightly more than $3 million on its own.

Calero, who lives in Miami, said Chamorro's exclusion from the FDN leadership was decided unanimously because Chamorro had refused to cooperate with the directorate's other six members and had insisted on speaking out.

"We told him that we felt he has excluded himself," Calero said today. "This is a decision that was long overdue."

Meanwhile, Brooklyn Rivera, a Nicaraguan Indian rebel leader, was refused entry into Honduras yesterday, preventing him from making an attempt to promote unity with other Indian insurgents and possible peace talks with the Sandinista government, according to sources here in Miami and in Honduras.

[In Paris, Reuter reported that France has agreed to give about $1.73 million in aid to Nicaragua.]