On the eve of the 27th Soviet Communist Party congress, Valentina Pletnova used a press conference to air her gripes about the shortcomings wrought since the last party congress, under Leonid Brezhnev in 1981.

Government bureaucracies are stifling, shops poorly stocked and discipline at work is slack, she told foreign journalists in her hometown of Kostrama, 250 miles northeast of the Soviet capital. "We will criticize," she said. "Criticism leads to improvement."

The day after the congress started, Pletnova took her complaints to a higher authority: the audience of party delegates gathered here for the congress, which ended yesterday.

After President Andrei Gromyko spoke on Feb. 26, the 55-year-old factory worker grabbed the microphone and launched a wide-ranging attack on "inertia" among Soviet factory managers, shoddy equipment and the slow pace of industrial modernization. Declaring the Kremlin's central economic planners "guilty," she said, "Still we work like yesterday."

The audience of 5,000 delegates, including Soviet leader Mikhail Gorbachev, broke into applause.

One of about 70 delegates to speak at the congress, Pletnova, a brash, plain-spoken Russian, had spent 27 years picking up pointers for her first appearance before one of the world's largest gatherings of Communists. She had come to Moscow to listen to a stream of speeches at every party congress since 1959, when Nikita Khrushchev opened the 21st party congress.

Due to Gorbachev's "modesty" and no-nonsense style, the 27th congress "was the most productive," Pletnova said. In her view, the Soviet leader set the right tone in his 5 1/2-hour opening speech Feb. 25. She approved of his emphasis on self-criticism, discipline and accelerating industrial modernization.

"I'm in love with my leader," she said. "In love!" She added, "The whole speech filled my attention. I wasn't even sleepy."

In her own speech, part of which was broadcast on national television, Pletnova complained of outdated equipment and shoddy dyes supplied to her flax mill in Kostroma. The conditions are so bad, she said, that no one wants to work there.

The power of the podium produced results. When Pletnova telephoned home after the speech, she said she found that a dye supplier and others already had showed up at her mill and promised better equipment and supplies.

After the congress, Pletnova said, the tasks of delegates is to carry the spirit of the congress out to the 18.5 million Communists across the Soviet Union, to continue the campaign against drinking and bribery and for harder work. If anyone -- from the boss to the minister -- slips into inertia, she said, "they should be ousted and sent to work in an ordinary job."

As the congress ended, Pletnova pointed to one shortcoming. Speaker after speaker stressed the need to improve planning and goods, she said. But, "again," she added, "no one has said how to do it."