MOSCOW (AP) _ A Politburo member who suffered a humiliating defeat in parliamentary elections lost his job as Leningrad Communist Party chief Wednesday. He is the first Soviet leader to be ousted under popular pressure.

The Leningrad party Central Committee's decision to retire Yuri F. Solovyov on a pension is a critical step in ''developing the process of democratization of the internal life of the entire party,'' said President Mikhail S. Gorbachev, who attended the meeting.

Solovyov also is likely to lose his position as a non-voting member of the party's 20-person ruling Politburo since he no longer holds the Leningrad job that put him there.

Voters in Leningrad, the country's second-largest city, rejected virtually their entire party leadership in the March parliamentary elections. Solovyov's defeat was especially embarrassing because he ran unopposed and still could not win approval from 50 percent of the voters in this city of about 4.8 million people.

Speaking in an extraordinary television interview that included both Solovyov and successor Boris Gidaspov, Gorbachev said the decision to change leadership came in response to party members' dissatisfaction. Speakers at the committee meeting complained they were being left out of political life, Gorbachev said.

He said the Politburo decided he should go to Leningrad to discuss the situation with local people.

The president, who promoted Solovyov to the Politburo three years ago, also said the party is behind in its efforts to restructure the Soviet Union.

''Many things are not being solved in the proper time, and this is due to the fact that the party itself does not act in time,'' he said. ''It lags behind.''

Gorbachev's statement follows several days of similar comments in the Soviet press, including the Communist Party newspaper Pravda.

After the March election defeat of 12 members of the Leningrad leadership, a poll found 68 percent of the city's residents and 66 percent of its party members did ''not believe the current party leadership has the ability to radically change the situation in the city.''

Communist activists started a grassroots effort to call a meeting of all 600,000 party members in Leningrad to oust Solovyov. But activist Marina Salye said in a telephone interview Wednesday the recall effort won the support of only 11,000, and they needed 200,000 to force a special session.

Instead, Solovyov's ouster came at the hands of the Leningrad Central Committee, a policymaking party group that typically numbers several hundred, with Gorbachev leading the discussion.

Solovyov, seated nexted to Gorbachev in the television interview and appearing unruffled, said the most important task he leaves for his successor is increasing the authority of the party on a democratic basis and ''eliminating its complacency.''

In April, shortly after Solovyov's defeat, Gorbachev sharply reprimanded him at a Kremlin meeting for complaining that the party had lost its unity and was becoming ''a discussion club.''

Solovyov's successor, Gidaspov, is a 56-year-old doctor of chemistry who was elected to the Congress of People's Deputies in the parliamentary election, defeating more than 20 opponents. As the head of an enterprise that runs joint ventures of several industries without interference from Moscow ministries, he is a leader in economic experimentation.

In the television interview, he smiled several times and said his election as Leningrad party chief over two other nominees came as no surprise.

''Nobody talked to me, not in Moscow, not in the Central Committee, not Gorbachev,'' he said. ''This is the choice of Leningraders.''

He promised to open discussion of the city's problems to a variety of groups, including environmentalists. He also said 18th-century central Leningrad, now marked by crumbling pastel facades, should be restored.