By SELWYN RAAB

A Cuban defector has told Federal and New York State law enforcement officials that agents of the Cuban Government conducted narcotics trafficking in the New York metropolitan area and in Florida in 1980 and 1981.

The defector, Mario Estebes Gonzalez, was arrested on drug charges 16 months ago. Since then, in testimony in Federal District Court in Miami and in statements to officials, Mr. Estebes has said his chief mission on behalf of the Cuban Government was to distribute cocaine, marijuana and methanqualone tablet in New York, northern New Jersey and Florida.

He has testified that he delivered between $2 million and $3 million to Cuban officials from proceeds of drug trafficking in the United States in a 15-month period.

Mr. Estebes told Federal officials that he and about 3,000 other Cuban agents entered the United States among 125,000 refugees who were allowed to leave Cuba from the port of Mariel in the spring of 1980.

In return for his cooperation, he is being protected by the Federal Government and has been granted immunity from prosecution for some narcotics trafficking he has admitted.

In Washington, Miguel Martinez, the first secretary and press spokesman of the Cuban Government's interest section in Washington, declined to comment on Mr. Estebes's allegations. The United States and Cuba have no formal diplomatic relations, and there has been no comment from Havana about Mr. Estebe's's arrest and statements.

Richard D., Gregorie,, who is charge of the narcotics section for the United States Attorney's office in southern Florida, said Mr. Estebes's allegations about the Cuban Government's complicity in narcotics trafficking were "very credible."

Many aspects of Mr. Estebes's statements have been "independently corroborated," Mr. Gregorie asserted in an interview.

Officials in the Justice and State Departments gave various explanations for the Cuban Government's purported role in drug deals. The officials offered these theories about why the Cubans had become involved in drug trafficking in the United States: to obtain hard foreign currency for use in international trade; to retaliate against American trade restrictions on Cuba; to cause social unrest in the United States, or to help finance leftist movements in Latin America.

The 33-year-old Mr. Estebes was arrested by the Coast Guard on Nov,. 29, 1981, while he was transporting 2,500 pounds of marijuana in a speedboat off the Florida coast.

Mr. Estebes was indicted on a charge of possession of marijuana with intent to distribute and he faced a maximum term of 15 years in prison. Because he was cooperating, he got a nine-month prison sentence.

Mr. Gregorie, an assistant United States attorney, said Mr. Estebes voluntarily admitted his role as a Cuban agent and gave Federal officials details of how Cuban officials arranged the drug trafficking. "It was a fortuitous break; we had no idea who he was," Mr. Gregorie said.

Mr. Estebes told Federal officials and investigators from the New York State Senate's Select Committee on Crime that he believed that about 3,000 other Cuban Government agents had entered the United States as refugees in the emigration of Cubans from Mariel.

Mr. Estebes, the officials said, maintained that the agents had a variety of assignments, including drug trafficking, disrupting Cuban exile groups, and economic espionage.

Mr. Estebes was a principal witness for the prosecution at a trial in Federal District Court in Miami in February that ended in the conviction of five men accused of smuggling narcotics into Florida. The drugs, he testified, were brought by ships from Colombia to the small port of Paredon Grande on the north shore of Cuba in the Old Bahama Channel. There, the drugs were unloaded and transported in small boats to Florida.

In the same case, four Cuban officials, including the commander of the Cuban Navy, Vice Adm. Aldo Santamaria Cuadrado, were indicted on conspiracy charges last Nov, 5. Since the United States has no diplomatic relations with Cuba, the Justice Department has no means to extradite the officials to stand trial.

Mr. Estebes, who is now being guarded in an undisclosed place by Federal agents, is expected to be given a new identity and placed in the Federal Witness Protection Program, Justice Department officials said. A spokesman for the department said Mr. Estebes might be a witness in other narcotics trials and therefore had declined to be interviewed.

Mr. Estebes is scheduled to testify at a public hearing in Manhattan tomorrow about drug trafficking in New York City and northern New Jersey.

The hearing, which has been called by Senator Alfonse M. D'Amato, Republican of New York, and the State Senate Select Committee on Crime, will also review charges that the Cuban Government released thousands of people imprisoned for violent crimes and allowed them to enter the United States by boat from Mariel in 1980.

The chairman of the crime committee, State Senator Ralph J. Marino, Republican of Oyster Bay, L.I., said one purpose of the hearing was to obtain Federal help for communities that have drug and other crime problems created by criminals who entered the United States as refugees in the emigration from Mariel.

New York City Police Department record show that from May 1980 through last December, people who are believed to have entered the country in the Mariel exodus have been arrested on charges of 6,288 felonies and misdemeanors. There are no accurate figures on how many of the Mariel refugees have been convicted of crimes in the United States.

Verne Jervis, a spokesman for the Immigration and Naturalization Service, said Cuba had refused to accept the return of Mariel refugees convicted of crimes in this country.

The hearing tomorrow will begin at 9:30 A.M. At the Federal Court of International Trade at 1 Federal Plaza.

Mr. Estebes was questioned in Miami through a Spanish-speaking interpreter by investigators from the crime committee on March 19. In a report to the committee, the investigators said Mr. Estebes told them that drugs obtained by Cuban agents in Florida were transported to dealers in New York City and to Newark, Elizabeth and Union City in New Jersey.

According to the report, Mr. Estebes said heroin and other narcotics were shipped to the New York area inside vans with concealed compartments to hide drugs.

"We have checked out Estebes's credibility with the Justice Department and the Drug Enforcement Administration, and they are satisfied he is telling the truth," said Senator Marino.

In accounts of his background to Federal and state investigators, Mr. Estebes said he was born in Havana and had been trained as a naval mechanic. He said he was employed by the Special Bureau of Missions in the Cuban Ministry of the Interior when he was instructed in the spring of 1980 to enter the United States on a boat from Mariel.

Records in the Community Relations Service of the Justice Department, which supervised the relocation of Cuban refugees, show that Mr. Estebes was released from a refugee camp at Fort Chaffee, Ark., on June 4, 1980. There is no record of when he arrived in the United States.

Mr;. Gregorie, the assistant United States attorney, said Mr. Estebes's first assignment from Cuba's Ministry of the Interior was to join Alpha 66, an exile group opposed to the Government of Fidel Castro. According to Mr. Gregorie, Mr. Estebes said he was directed to sabotage boats used by the group for missions to Cuba.

Mr. Estebes said his assignment at Alpha 66 was soon changed, according to Mr. Gregorie.

Mr. Gregorie said Mr. Estebes indicated that in August 1980 he underwent a brief drugs training program in Cuba and returned to Florida with a list of contacts in the illegal narcotics trade. Before his arrest, Mr. Estebes said, he had access to speedboats and traveled frequently to and from Florida and Cuba, a distance of about 100 miles.

"He ran narcotics, and he was told to bring in as many drugs as possible," Mr. Gregorie said. "He said he told his superiors in Cuba: "I'm a goo soldier. If that is what you want me to do, I will do it."

According to Mr. Gregorie, Mr. Estebes said he delivered between $2 million and $3 million in cash to his control officers at the Interior Ministry in Cuba.

Mr. Gregorie said it would be inaccurate to describe Mr. Estebes as a spy. "He was really a narcotics runner for the Cuban Government," Mr. Gregorie said. He said that when Mr. Estebes was asked by the Federal investigators why he had admitted his role as an undercover agent, Mr. Estebes replied that "I am tired of helping Cuba do this - bring in drugs."

At the narcotics trial in Miami in February, Mr. Estebes testified that he saw Admiral Santamaria give orders permitting the unloading of narcotics at Paredon Grande brought in by reputed international trafficker in drugs, Jaime Guillot Lara. Mr. Guillot Lara, a Colombian, has been indicted on Federal drug charges and is a fugitive, according to the Justice Department.

The Drugs, Mr. Estebes testified, were later smuggled into Florida.