The hottest political issue in India these days is who was the CIA informer in Indira Gandhi's Cabinet during the 1971 War in Bangladesh.

The question was raised 11 days ago by Gandhi, who is making a comeback after suffering a humiliating defeat in the March 1977 elections. So far she has embroiled both of the political parties opposing her while managing herself to stand clear.

The American CIA is used routinely as a whipping boy in Indian elections. This time, the ammunition was handed to Gandhi on a silver platter in the form of a biography by Thomas Powers, of former spy chief Richard Helms, entitled "The Man Who Kept the Secrets."

In the book, which is not yet avialbale here, Powers tells how in August 1971, an informer in Gandhi's Cabinet told the CIA that the Soviet Union had signed a friendship treaty with India to forestall Indian recognition of Bangladesh.

Later that year, with India fighting Pakistan in Bangladesh -- then East Pakistan -- the Cabinet member was able to answer a CIA question and report that the Indians planned to extend the war to West Pakistan.

According to Power's book, Nixon called the information one of the most timely pieces of intelligence he ever got from the CIA.

In addition, four leading politicians in the two anti-Gandhi parties were members of her Cabinet in 1971. One of them, Jagjivan Ram, defense minister in 1971, has denied a public accusation that he was the CIA informer.

Another, Deputy Prime Miniter Y. B. Chavan, finance minister in 1971, announced that several government ministries are running a coordianted investigation to uncover the CIA informer.

Ram and Chavan are major figures in the Janata and Lok Dal parties, the major opponents of Gandhi's Congress Party in the Jan, 3 elections. Splinters of the coalition that defeated her in 1977, they now spend as much time fighting each other as they do battling her party.

Ram, the undisputed leader of India's Untouchable caste, is the only Janata leader who was in Gandhi's 1971 Cabinet. But there are three Lok Dal members -- Chavan, C. Subramanian, the present defense minister, and Karan Singh, the present education minister -- who were in that Cabinet.

Charan Singh, the caretaker prime minister and head of the Lok Dal, has said that no members of his present Cabinet was the CIA informer.

Oddly enough, none of the information revealed in Powers' book was new. Columnist Jack Anderson reported in 1971, when he uncovered the Nixon-Kissinger "tilt toward Pakistan," that the CIA received information on Indian intentions from a member of Gandhi's Cabinet.

In fact, Powers included the information in his book as an illustration of how upset the CIA was about intelligence leaks from high in the executive branch. The CIA, Powers wrote, "was not about to tell every junior desk officer in government that it had an agent in Indira Gandhi's Cabinet."

When Gandhi told a Nov. 10 political rally in Kampur about the CIA informer in her Cabinet, she said she had not seen the book but had been sent a copy of the section involving her.

Two days later the Ministry of External Affairs, on the direct orders of Foreign Minister S. N. Mishra, released the excerpt.

Since then, Prime Minister Singh's caretaker government has been trying to pin the charge of CIA agent on Ram. Singh hinted that Ram was the man who informed the CIA, and on Monday one his political allies, Raj Narain, actually named Ram.

Only one newspaper, the Express, carried the story. One news agency also carried Narain's charge, but later asked subscribers to kill the name.

Narain, the president of Singh's Lok Dal party whom the Express described as not having "distinguished himself by sobriety" in his post, offered only one piece of circumstantial evidence to back the charge: the fact that Ram left the post of defense minister after India defeated Pakistan and became agriculture minister.

That, Narain said, could indicate that Gandhi knew that Ram was feeding information to the CIA.

In denying that charge, Ram attacked Singh for clearing members of the present Cabinet before the goverment investigation is completed and defended his record as a member of the Gandhi Cabinet.

"I have dealt with the defense apparatus of the country for several years and I have dealt with it to the satisfaction of the entire nation," he said.

While the Janata and Lok Dal politicans battled each other, Gandhi has been sitting quietly on the sidelines. She was acused of having CIA connections in a book by Sen. Patrick Moynihan (D-N.Y.), the former U.S. ambassador to India, who wrote that Gandhi's Congress Party received CIA funds twice in the past.

The newspapers, however, have roundly condemned all the politicans for raising the CIA issue. The generally pro-gandhi Times of India last week called it "shocking" that Gandhi "lent credence to the charge that an unnamed Cabinet colleague was in touch with the CIA." Later, in an editorial headed "From Bad to Worse," the Times attacked Narain and Singh for pointing the finger at Ram.

The Times editorial also defended its position of not printing Narain's original charge, which it called "libelous . . . to a hghly respected individual who can be the country's prime minister one day."