Communist Party Chairman Hu Yaobang today lashed out at China's political and literary dissidents, threatening serious reprisals for those who fail to toe the party line.

In a speech seen as the most authoritative guide to communist literary policy and party discipline in recent years, Hu described his targets as "dark phenomena in our present socialist society" and pledged "an unrelenting struggle against these evils."

Hu singled out for special criticism party cadres in economic fields who have failed to carry out new pragmatic reforms to spur China's sluggish economy, calling them "highly irresponsible bureaucrats... who lack a comprehensive view" of the national interest.

Other government officials, said Hu, "disgrace the country" by using their power to "feather their own nests" and solicit bribes from foreigners. Hu apparently was referring to Chinese trade officials who have accepted gifts from foreign businessmen seeking contracts.

"All such negative elements must be dealt with seriously," warned the party chief, recommending a steady diet of public criticism of wayward party officials until they repent and correct their ways.

For China's writers who "lack faith in the socialist system," said Hu, the party should respond with stiff criticism. He prescribed stronger medicine for the tiny group of dissident writers who show "an ingrained hatred for new China, socialism and the party. Although they are few and unusual, the party must remain on guard against them. It would be dangerous to underestimate them. They ought to be punished by law for counterrevolutionary activities."

Hu's first important public speech since becoming party boss three months ago was seen by diplomatic analysts as the most definitive statement on party policy toward insubordinate officials and writers.

Diplomats viewed the speech, delivered before party leaders at the Great Hall of the People, as part of efforts to obtain the kind of stability top officials believe is necessary to ensure economic recovery.

The speech came at a time when the nation's highly touted economic retrenchment plan has produced mixed results. Although the outlook is bright for agriculture and light industry, planners have been discouraged by a negative growth rate in heavy industry for the first half of this year.

Hu and his moderate allies who have run China since the 1976 death of Mao Tse-tung have sought to root out Mao's radical followers in the bureaucracy who oppose use of material incentives and decentralization of decision-making.

Moderate leaders blame their old radical foes for sabotaging economic policy together with unsympathetic artists who are accused of fracturing and demoralizing workers by emphasizing China's problems and extolling the virtues of foreign countries.

Although Hu's speech today at the centennial birthday rally for the late author Lu Xun was mostly aimed at contemporary writers, the party chairman pointedly criticized "certain leading party cadres...cut off from reality and the masses.

"They neither study problems nor solve them," he said at the rally of 6,000 party officials. "They stick to old rules, show no interest in necessary reforms. They dispute or refuse to carry out tasks that do not benefit their departmental interests or are not to their liking.

"This is the mistake of selfish departmentalism, which injures the whole country's interests while claiming to represent the interests of the masses."

On literary policy, Hu presented the clearest and sharpest attack by a top party official in a year of fluctuating guidelines that has seen one well-known playwright savagely criticized by an Army newspaper and then given an award by a party committee all within a few weeks.

Emphasizing the writer's role as one of cheerleader for the party and socialism, Hu divided wayward authors into four categories and suggested remedies for making them productive social forces.

Except for dissident critics who should receive the strong arm of the law, he recommended a blend of "persuasion and criticism" for the other three categories -- writers who were mistreated in the past and nurse grudges against the party, writers who publish their social complaints and writers who cannot accept socialism intellectually.

Although most writers understand the importance of literary guidelines, said Hu, others at home and abroad will grow apprehensive because of past persecution of artists during the Cultural Revolution.

"There are poisonous weeds and beautiful flowers," said the chairman. "If we let poisonous weeds and beautiful flowers grow together without the requisite struggle, then there will be chaos in our art and literature."