NEW DELHI, SEPT. 1 -- Scores of government agents across the country today raided offices of the Indian Express, the newspaper group that has taken the lead in a campaign against alleged corruption in the government of Prime Minister Rajiv Gandhi.

Gandhi recently has shown some signs of weathering a political storm generated by the long-running debate on corruption but he came under sharp criticism this evening from leading editors and opposition political leaders.

The raids were a "deliberate government attempt to intimidate one of the country's leading newspapers, which lately has been attacking it on many counts. This endangers freedom of the press and cannot be taken lightly," said the Editors' Guild of India, an independent organization of 80 to 90 leading newspaper editors.

The statement was issued by the group's general secretary, H.K. Dua, editor of the Hindustan Times, which is a rival to the Indian Express. It said, "Whatever the reasons" given "to explain the decision to launch the raids, . . . the government's motive is too clear to hoodwink anyone. The fact the raids have taken place only a day after Parliament adjourned speaks for itself."

A statement issued by B.V. Kumar, director general of the Directorate of Revenue Intelligence, the government's main tax-enforcement agency, said the government had "received information" indicating widespread violations of customs, foreign exchange and import regulations, mostly to do with the import of printing equipment by the Express and related companies.

In addition to waging a campaign against alleged payoffs in defense deals, the Express has charged that close political allies of the prime minister are guilty of similar violations.

India is one of the few Third World countries with a vigorous and relatively free press. With the country's political opposition fragmented, the press has taken on an ever larger role in recent years as watchdog on government activities.

In 1975, when Gandhi's mother, Indira Gandhi, who was then prime minister, declared a national state of emergency, a number of editors were among those taken into custody and newspapers were heavily censored. The Express offices also were raided during those politically troubled times, as they were earlier this year following publication of a supposedly private letter from then-president Zail Singh sharply criticizing the prime minister.

The 1975 "emergency" ultimately rebounded against Indira Gandhi, causing her defeat in elections in 1977, and political observers said today that the raids against the Express likely will give new ammunition to a movement being led by former finance minister V.P. Singh to throw out the Gandhi government.

Leaders of the opposition Janata and Bharatiya Janata parties quickly called the raids an "attack on press freedom."

"These raids are intended on one hand to gag the Indian Express, and on the other to serve as a warning to the rest of the print media that if they persist with their exposures about the scandals relating to submarines, Swedish guns and Swiss bank accounts, they too would be in for trouble," L.K. Advani, president of the Bharatiya Janata Party, said.

India's radio and television are government-controlled and rarely carry news critical of officials or the ruling party.

Ramakrishna Hegde, chief minister of Karnataka State and one of the country's few opposition figures with national standing, joined in the outspoken criticism, calling the raids "shameful and strangulation of press freedom."

The chorus of sharp statements comes at a time when the prime minister has just gone through a session of Parliament relatively unscathed by opposition attacks over allegations of illegal payoffs in the purchase of heavy artillery from Sweden and submarines from West Germany.

Recent polls have shown that although the corruption issue is widely recognized in the country, including rural villages, the prime minister and his party retain sufficient political support to win an election were one to be called. He does not have to go to the polls until 1989.

Barring major revelations implicating Gandhi or family members in a coming Swedish government probe of the sale of artillery to India, his short-run prospects had appeared reasonably secure, although his longer-term hold on the Congress (I) Party and the party's hold on government remain uncertain.

Former finance minister Singh and several other political leaders who have fallen out with Gandhi in recent months have been mounting a campaign of speeches and political rallies around the country on the corruption theme.

The large crowds at the rallies appear to have Gandhi and his aides concerned.

Indian Express editor Arun Shourie, an outspoken critic of the prime minister, linked today's raids on Express offices with the corruption campaign.

"This goes to show that the prime minister is directly involved in the Bofors {artillery purchase} controversy," he said.