At the close of a six-day Communist Party conference, China's top leader Deng Xiaoping today called for continued economic reforms but at the same time urged party members to tighten discipline and intensify their study of Marxism.

Confronting the first open criticism of his policies at the conference, Deng described the overall situation in China as "good" but also touched on what he considered problem areas, including economic crimes, a lack of effective ideological work at the Communist Party's grass roots, and a failure to reduce to a minimum "the pernicious influence of capitalism and feudalism."

"We should continue to crack down on serious criminal activities and prohibit all decadent practices that undermine standards of social conduct," said Deng, adding that state enterprises and institutions "absolutely must not harm nor extort from the people."

Deng proposed that leading party cadres renew their studies of Marxist theory.

Some observers saw Deng's emphasis on discipline and ideology as evidence of a compromise, with the pragmatic Deng moving toward harder rhetoric in exchange for getting his way in the current party meetings on most personnel changes. Some saw it as part of Deng's well-known ability to coopt his opponents, taking two steps forward and one step back.

A western diplomat pointed out that Deng has always been a strong advocate of discipline and that party meetings require references to Marxist ideology.

"At high-level party meetings, you have to go back to the basics at some point," said the diplomat. "You've got to go back to the old-time religion."

Diplomats have been impressed with Deng's ability to obtain sweeping changes in the personnel of the party's leading organizations. The biggest test is expected to come Tuesday when a newly constituted party Central Committee is to name new Politburo members.

But today the first visible sign at the party conference of opposition to the fast pace and wide scope of change came into the open with a speech by Chen Yun, the party's senior economic planner and a member of the powerful Politburo standing committee. In terms much stronger than those employed by Deng, Chen Yun stressed the need for a planned economy and warned of a number of "serious violations" of party discipline. He accused some party members of forsaking communist ideals.

Chen Yun, 80, began his speech by saying that he endorsed the succession, which Deng orchestrated, of younger officials to positions in leading Communist Party organizations. This seemed to be a major concession on Chen Yun's part to Deng's plan for an orderly transfer of power to younger cadres who will carry on the program.

But Chen Yun then immediately launched into a criticism of the impact that rural economic reforms have had on grain production. He said that so many peasants were going into small businesses and industries that it had detracted from the production of certain crops, including grain. He cited a Chinese saying: "Grain shortages will lead to social disorder."

The rural economic reforms permitted peasants to go directly to the market with some of their products and to sell fewer of their products to the state. On the free market, grain sells at a lower price than most crops, so peasants turn to growing more profitable crops.

Chen Yun was the party's chief economic planner in the 1950s. He opposed the late chairman Mao Tse-tung's disastrous Great Leap Forward in the late 1950s, and his effective powers were removed during the 1966-76 Cultural Revolution. Deng helped bring him back to power in the late 1970s. He and Deng are not opponents, but Chen, who was the architect of the economic "readjustment" of 1980-82 in which ambitious economic goals were scaled back, seems to be constantly in the position of advocating more caution in the reforms.

"The planned economy's primacy and the subordinate role of market regulation are still necessary," said Chen. "Market regulation involves no planning, blindly allowing supply and demand to determine production."

And, as if anyone needed to be reminded, Chen said, "We are communists. Our goal is to build socialism."

On the subject of corruption, Chen was scathing.

"There are now some people, including some party members, who have forsaken the socialist and communist ideal and turned their backs on serving the people," he said.

"In pursuit of their own selfish gain, they 'put money above all else,' regardless of the state's and people's interests . . . . Some of them have become rich by unlawful means such as speculation and swindling, graft and the acceptance of bribes."

He also touched on the delicate question of nepotism, a problem in China even before the Communists came to power.

Chen said he hoped senior party leaders would set a good example in educating their children. Those children, he said, "absolutely must not use their parents' positions in pursuing personal power and interests . . . ."