Indian Prime Minister Rajiv Gandhi, fresh from winning an unprecedented three-fourths majority in Parliament, today formed a government with a new-look Cabinet.

Gandhi dropped three Cabinet-rank ministers whom he had carried over from the government of his mother, Indira Gandhi, following her assassination two months ago, and added five new ministers to a Cabinet whose accent appears to be on youth and progressive managerial skills.

Among those dropped was finance minister Pranab Mukherjee, Indira Gandhi's senior Cabinet minister, who under the traditional line of succession would have become prime minister on Oct. 31 had the party leadership not decided to continue the family dynasty. Also dropped without explanation were railways minister A.B.A. Ghani Khan Choudhuri and justice minister Jagannath Kaushal, who were considered vulnerable because of ineffective management of their ministries. Talking with reporters after the swearing-in ceremonies in the stately president's mansion, Gandhi said he had set three criteria for his ministers: that they be efficient, have integrity and produce results.

When asked if any of the ministers who had been dropped would be returned to the government later, Gandhi replied, "No, no. Why should they be brought back?"

Addressing a joint meeting of Congress (I) legislators in the newly formed Lok Sabha (People's House) and the largely ceremonial upper house, the Rajya Sabha, Gandhi said the greatest task before the new government was "to improve the condition of poor people. I will need all your help to carry this massive mandate." Pledging a "clean and efficient government," the new prime minister said: "Our politics should be clean. The development should be speedy and the fruits of development programs should reach to the people." He stressed that India needed modernization not only in science and technology, but also in the administrative system.

As deputies thumped their desks in support, Gandhi resolved to harness the energies of the youth and the women of India in a "larger measure in the nation-building task."

The prime minister appointed 14 Cabinet ministers and 23 ministers of state, eliminating the traditional third tier of deputy ministers in the Council of Ministers because, he said, "actually, the deputy ministers had no work."

The new ministers of state include Arun Nehru, a cousin and close confidant of the prime minister who is characteristic of the inner circle of young, successful businessmen with whom Gandhi has surrounded himself. Also named ministers of state were two career diplomats regarded as part of the progressive generation of the foreign service, K.R. Narayanan, former ambassador to the United States, and Natwar Singh, secretary of the Foreign Ministry.

The new members of the 15-member Cabinet are Abdul Ghafoor, former chief minister of the northern state of Bihar, works and housing minister; Asoke Sen, a constitutional expert and former law minister, minister of law and justice; Bansi Lal, former chief minister of Haryana state, railways minister; Vishwanath Pratap Singh, head of the Uttar Pradesh state Congress (I) Party and former member of Indira Gandhi's Cabinet, finance minister, and K.C. Pant, a one-time energy minister, named as education minister.

There were 49 members of the outgoing Council of Ministers. Seven were defeated in last week's elections, three ministers of state were denied tickets by the Congress (I) Party and one died on the eve of the polling. This left Gandhi room to bring in some new faces, while retaining most of the former senior ministers he inherited from his mother's government.

President Zail Singh administered the oaths in English in the imposing Ashok Hall of the president's mansion.

Earlier in the day, Gandhi was unanimously elected leader of the Congress (I) parliamentary caucus, a formality that just two months ago was hurriedly carried out by the inner circle of the leadership in an atmosphere of grief and solemnity following the assassination of his mother.

Today, however, the cavernous, floodlit central hall of Parliament reverberated with thunderous applause and shouts of "Rajiv Gandhi, zindabad!" or "Long live Rajiv Gandhi," as his jubilant party endorsed the 40-year-old former airline pilot for the leadership of a political movement forged four decades ago by his great-grandfather, Motilal Nehru, and his grandfather, Jawaharlal Nehru, India's first prime minster after its independence from Britain.

With all but three of the 508 contested Parliament seats declared, the Congress (I) Party has won 398 seats. With its allies and the seats it is expected to win when elections are held for the rest of the total 542 elective seats in Parliament, the Congress Party will be well over a three-fourths majority.

Before the first session of the new Parliament was convened, the members stood in silence for two minutes to pay tribute to Indira Gandhi, who was gunned down by two Sikh security guards Oct. 31, after leading the nation for 16 years.

After Home Minister P.V. Narasimha Rao, a longtime confidant of Indira Gandhi, nominated her only surviving son to the parliamentary leadership, and after the members voiced their unanimous approval, Parliamentary Affairs Minister Buta Singh asked the deputies if they had any other motions. The chamber echoed with a chorus of "No!" Gandhi, who won by 300,000 votes in his parliamentary race in Uttar Pradesh against his estranged sister-in-law, Maneka Gandhi, automatically began a new five-year term as prime minister.