The tale of Mateusz Birkut, a hero worker of the Stalin-era in Poland who landed in prison because integrity made him a political nuisance, has captivated Poles this spring, providing, they say, a remarkably honest portrayal of how things were - and are.

The Birkut story (fictional although based in large measure on real events) is a movie called "Man of Marble" by Andrzej Wajda, 51, Poland's leading filmmaker and acknowledged as one of the world's very best directors. Using a script that has been untouchable for more than a decade, Wajda has done what is probably his finest work and certainly his most daring.

The plot evolves ingeniously through flashbacks as a young woman, completing her course at a film school, searches out what happened to Birkut 25 years earlier to make a documentary about him. The ending is ambiguous, but the implication is that her discoveries are considered too explosive by the head of the school and her movie will not be accepted.

To understand the effect of "Man of Marble" on audiences here, consider the sensation that "Roots" caused this spring in the United States with its dramatized examination of sensitive issues in American history. The subject of the Wajda film is wholly different of course, but the impact of looking frankly into a painful past is similar.

Poles are stunned when they see the cynicism and opportunism behind worker glorification, the travestics of justice and fear of honesty portrayed on the screen. Such things do not get presented lightly in Poland where the state determines the bounds of ideological propriety.

Indeed, there were a host of rumors when the movie appeared in March that it would immediately be withdrawn. The result was that huge crowds gathered in the streets outside the two Warsaw theaters where it was being shown and the tickets were black-market priced at about 10 times their regular value.

But a decision was plainly made - Poles are certain that Communist Party leader Edward Gierek himself was responsible - to let "Man of Marble" stay on for as long as it could attract audiences. The film then opened in cities elsewhere around the country and is still playing. Entry now is relatively easy, in Warsaw, at least, although houses continue to be full.

The reason so politically revealing a film has been released at this time - Poland has often produced films that are artistically notable - seems to go to the very core of the country's current situation.

Poland was severely jarred last June when food price rises set off a wave of worker violence and strikes that forced the leadership to rescind the increases overnight. Recognizing that repression would surely lead to further trouble, the authorities have sought instead to deal with the discontent that the riots showed not only among workers but among farmers, the powerful Catholic church and the intelligensia as well.

To the intelligentsia in particular, confronting the realities of Polish society past and present, even when that runs counter to truth as the party would like it known, is as important as stable prices are to the population at large and an end to harassment is for the church. "Man of Marble" is therefore an important gesture by the leadership. But Poles wonder if it means anything more than just a gesture - perhaps, some hope, a change of official attitude.

Wajda, whose previously most successful films were "Ashes and Diamonds" and Kanal," done during a period of cultural thaw in the late 1950s, seems prepared to test the limits of what is permissible now. "Man of Marble," the director told a Warsaw literary weekly, is one of several movies to appear lately in Poland that "say something other than just what a fine artist one is."

His next film - Wajda was in the United States last winter directing a Polish play called "White Marriage" at the Yale Repertory Theater that got rave reviews - though I still don't know what it will be about, will cartainly be a continuation of the way of showing things applied in my last film.

Mateust Birkut, the "Man of Marble" for whom a statue is erected and later pulled down, is a young bricklayer who is prodded by local party officials to lay 30,000 bricks on a single shift at a steelworks under construction near Krakow about 1950. The feat is filmed and Birkut is promoted into a national figure, sent travelling around the country showing off his skills as a symbol of the patriotic proletariat.

One day, someone passes him a redhot brick and his hands are permanently scarred. When his best friend is accused of the crime, based apparently on evidence supplied by a security policeman assigned to follow Birkut's every move, the bricklayer is appalled. He desperately tries to help his friend and even goes to the party central committee in Warsaw. At every step, officials warn him to keep silent. After he attempts to protest openly at a party meeting a microphone plug is pulled and the audience breaks into a loud chorus of a Polish anthem.

Birkut himself is seized and there is a dramatic scene - done in the format of an old, unused piece of newsreel film - in which he appears at a show trial where his friend stands accused of subversion and reveals how police have tortured him. After the 1956 upheavals in Poland and elsewhere in Eastern Europe when more liberal leaders take over, Birkut (and the friend) are released. Once again efforts are made to turn him into a hero, this time to the benefit of the new regime led by Wladislaw Gomulka. He resists, is finally forgotten and dies.

His son is discovered working as a dockhand in Gdansk by the film student investigation Birkut's life. Gdansk is symbolically important because of the worker unrest there in 1970 that led to Gomulka's downfall and his replacement by Gierek.

Many of the characterizations are striking: The security policeman who turned in Birkut's friend is now the greasy manager of a night club in Warsaw selecting girls for strip-tease numbers; the friend himself is a confirmed apparatchik mouthing the same empty platitudes as everyone else. The young filmmaker is a breezy blonde in denim whose father looks at her and wonders how she will ever find a husband dressed that way.

Most stirring of all to many younger Poles is the director of the film school who for all his well-tailored suits, his ascot, his French sunglasses, his frenetic, well-traveled sophistication succumbs in the end - or so we are led to believe - to political prudence. Wajda, however, has not.