A defector identified yesterday by the State Department as a major in Cuba's intelligence service has described his crossover to the United States as part of a widespread revolt by agents against massive spending by President Fidel Castro on spy activities.

Maj. Florentino Aspillaga Lombard, 40, defected June 6 by entering Austria from Czechoslovakia, where he was serving as an agent, according to the State Department, which said it would offer no other information.

The U.S. Information Agency's Radio Marti, however, detailed the case of Aspillaga after broadcasting to Cuba the first part of an interview with him on Sunday. In it, he detailed charges of corruption in high places, described dealings with the current military chief of Panama, and offered the first inside explanation of leadership changes in the Ministry of Interior.

Castro's close friend and companion in the revolution, Ramiro Valdes, was ousted as minister of interior in December 1985 and removed from the Politburo of the Communist Party last year without explanation. Aspillaga said Valdes, who came late to the party, lost a power struggle with Castro's brother and second in command, Raul, who is head of the armed forces.

Diplomatic sources in Havana speculated last month that Valdes was removed as part of Castro's crackdown on corruption. Aspillaga indicated, though, that Raul Castro moved against Valdes to protect a colleague, who was chief of intelligence, and who the defector said spent "thousands of dollars on imported whiskey."

At the same time, Aspillaga said, Valdes was spending the peso equivalent of more than $100 million on a secluded housing complex for ministry staff "when there is no housing for the people."

Aspillaga said that he was the control officer for double agents who were presented on Cuban television last month. He said the broadcasting was an effort to use agents whose covers he had blown for propaganda purposes.

Saying he spoke for a band of agents still on the job, Aspillaga charged that in a diversion of funds following the 1983 U.S. intervention in Grenada, Cuba now maintains 2,086 intelligence officers at home, in several Latin American countries, in African countries where Cuban troops serve, in France and Spain, and in the Soviet Bloc. This is costing millions, he said, and "we are against all this."

As for the current interior minister, Jose Abrahantes Fernandez, Aspillaga said his children are leading "la dolce vita" in Moscow. He charged that the minister has a close association with Panamanian Gen. Manuel A. Noriega and through him supplies arms to Nicaragua and recipients in El Salvador and Honduras.

Denouncing what he termed Cuba's new "Fidelista religion," Aspillaga charged that Castro maintains houses in all 14 provinces, several yachts and a Swiss bank account. The defector said Castro has four children, all studying in Mosocw. Castro has claimed publicly only one child, Fidelito, 37.