MOSCOW, JUNE 25 -- Soviet leader Mikhail Gorbachev, in a major speech today to the country's leading policy-making body, criticized opponents of reform in the Communist Party and government bureaucracy for lagging behind the "economic, social and spiritual" process in the country and called for drastic changes in the Soviet economy to be carried out by the end of this year.

The 56-year-old head of the Soviet Communist Party, who admitted that his first two years in power had produced only "insignificant" changes, outlined plans for a major reorganization of the Soviet economy that would involve "radical" change in the pricing system, a revamping of the central planning mechanism to grant more responsibility to managers at the local level and no limits on what workers can earn.

The strongly worded speech, delivered before a regular meeting of the 307-member party Central Committee, marks a new phase in Gorbachev's program of restructuring the Soviet economy as he shifted his reform strategy away from piecemeal change to focus on the transition from an "excessively centralized command system" to one of greater "self-management."

The Soviet leader also singled out the armed forces for its failure to respond to demands for reform and greater efficiency. Alluding to "negative trends" in the country's defense establishment, he noted the lapse in Soviet air defenses that enabled West German teen-ager Mathias Rust to fly unimpeded through 400 miles of Soviet airspace before landing in Moscow's Red Square.

"The imbalance between the growing vigor of the masses and the still surviving bureaucratic manner of activity in most diverse fields and attempts to freeze the renewal drive is one of the manifestations of this real contradiction," Gorbachev said.

"The same is also evidenced by the violation of Soviet air space by the West German sports plane and by its landing in Moscow. This is an unprecedented occurrence from all points of view," he said.

Defense Minister Sergei Sokolov and other leading military officials were fired after the incident. Rust remains in a Soviet jail while the investigation into his flight continues.

The central problem facing the country, Gorbachev said in one summary of the speech released tonight by the Tass news agency, is "the ineffectiveness of the economic mechanism, the system of management."

"Much has been done but only partial results have been achieved. There are changes, but they are insignificant and not radical. The main work to form an integral system of managing the economy yet lies ahead."

Gorbachev warned the Central Committee, which represents the core of the country's leadership, that the party and the government were in danger of being outstripped by the people in the push for change.

"An alarming tendency has taken shape, comrades, and is borne out by facts -- a number of party organizations are lagging behind the dominant moods and the dynamic processes now developing in society."

In a passage that underscored his mounting impatience with the slow response to initiatives from above, Gorbachev noted that two years ago the leadership had heeded pleas from top managers for time to put changes into practice.

"We said at the time that everyone was being given both time and a chance to readjust," he said. "But business, comrades, brooks no delay."

The plenary meeting, expected to continue at least one more day, will adopt a proposed law on state enterprises, which has been seen by some Soviet economists as insufficient. The Kremlin leader today said guidelines for a "radical reorganization of economic management," containing "fundamental and concrete provisions," will also be considered here this week and "should be adopted" before the end of the year.

Last January, at another meeting of the Central Committee, Gorbachev called for a broad program of "democratization" in all spheres of society, including the Communist Party, but his appeal was not endorsed in full by the committee.

However, since then, the drive for greater democratization has been widely promoted in the press, and factories and institutes have experimented with new ways of selecting their directors. Last week, scattered electoral districts around the country experimented with a system of multi-candidate balloting for local government offices.

Gorbachev today took a tough line with opponents of his program, accusing some critics of continuing, "by their inaction, actually to sabotage restructuring."

He put these opponents on notice with a proposal today for a new, single party control apparatus that will be given greater powers to combat abuse of office and economic crimes.

The Soviet leader also announced that a party conference will be held in June 1988, midway before the next regularly scheduled party congress. The gathering is expected to be a critical political milestone for Gorbachev.

Stepping up attacks on "preserves of inertia and sluggishness," he singled out several individual ministers and even regional party leaders for failing to carry through economic changes already adopted by the party and government. The most prominent figure criticized by Gorbachev was Nikolai Talyzin, an alternate member of the Politburo who heads the state Committee for Central Planning, or Gosplan.

Gorbachev also noted that the party has "awakened the activity of the masses, and it is our duty to prevent this upsurge from petering out."

Gorbachev emphasized the need for quick improvement in social conditions, which have not changed noticeably in the last two years, according to letters published in Soviet newspapers.

"People write that they are for renewal but that they see no changes around them," he said. ". . . This means that despite tremendous efforts the restructuring drive has in real fact not reached many localities. This, comrades, is a very serious symptom."

To give the public a stake in greater productivity, Gorbachev said, "it is particularly important that the actual pay of every worker be closely linked to his personal contribution to the end result and that no limit be set on it. There is only one criterion of justice: whether or not it is earned."

Higher wages for better workers will have no effect if goods and services continue to fall short of demand, he said. "This has now become the most acute political problem," he said.

Even the ruling Politburo, the 11-man group headed by Gorbachev, came in for criticism today. "I must say self-critically that we also see our weaknesses in practical work. There are instances when important decisions on major questions of the country's development are being fulfilled slowly and not in full volume," said Gorbachev.

In a rough outline of the package of reforms to be presented to the Central Committee, Gorbachev echoed themes in the Soviet press lately that "half-measures" will doom economic reform.

Gorbachev today called for: A "drastic expansion" of the rights of factories and enterprises in managing supplies and workers. A "radical transformation" of the central planning agencies, enhancing their strategic role, but relieving them of the day-to-day management of the economy. A "cardinal reform" of planning, pricing, financing and credit systems. A creation of "new organizational structures," to encourage better research and development in technology. Transition from "the excessively centralized command system of management to a democratic one," development of self-management and change in methods of work.