Soviet conservatives flex muscles, attack writer. Change continues in Mikhail Gorbachev's Soviet Union - though in fits and starts. A reform-minded playwright's latest works have been criticized for misrepresenting the Russian Revolution.

The playwright Mikhail Shatrov, one of the most outspoken supporters of radical political reform, has come under simultaneous attack in two major Soviet papers for political and historical mistakes in his two latest plays. The attacks seem to mark a new round in the intense debate between radical and conservative reformers over the nature of change, and provide further proof of the conservative reformers' strength.

A review of Mr. Shatrov's play ``Brest Peace'' in the Communist Party daily Pravda on last Thursday criticized the dramatist's lack of knowledge of the early days of the Russian Revolution.

A front-page editorial in the same issue states that ``even the slightest inaccuracies, juggling with the facts or departure from the truth'' are inadmissible when dealing with the life and work of Vladimir Lenin, the leader of the Bolshevik Revolution. The editorial does not name Shatrov, but probably few readers will fail to link the two articles. This is Pravda's second attack on Shatrov this month.

Also on Thursday, a long article by two historians in Sovietskaya Rossiya, an influential newspaper, ascribes to Shatrov the sort of mistakes that Pravda describes as inadmissible. The historians accuse Shatrov of presenting an oversimplified view of the 1917 Revolution in ``On, on, on,'' his latest and most-controversial play. The play appeared in the January edition of the literary journal Znamya.

Radical supporters of change have responded to the latest play in a markedly different way. ``If this can be published, things can't be too bad,'' one prominent reformer reportedly told Shatrov soon after the play appeared in print.

In ``On, on, on,'' Shatrov makes clear his belief that Soviet dictator Joseph Stalin was an unmitigated evil. Stalin was ``a criminal, the like of which the world has perhaps never seen,'' Shatrov told this correspondent and a colleague during a recent interview. Stalin's views had ``no relationship to communism,'' he added. ``If he was a communist, I would have to leave the party immediately.''

This runs counter to the views expressed last November by Soviet leader Mikhail Gorbachev. In a speech that disappointed some radical reformers, Mr. Gorbachev called for a balanced picture of Stalin's achievements and crimes.

Growing criticism of Shatrov has a significance that goes well beyond literature or history. The interpretation of the Soviet Union's 70-year past has become a major battleground between radical reformers and more-conservative members of the political establishment. Two key issues are implicit in the debate: the legitimacy of the Communist Party and its future role in transforming society.

More-conservative reformers apparently fear that excessive criticism - history as ``a chain of errors and disappointments,'' as second-ranking Soviet leader Yegor Ligachev has put it - will undermine popular faith in the party.

Gorbachev's November speech, with its carefully modulated assessment of Stalin, was interpreted by some prominent reformers as a sign that Gorbachev had moderated his support for radical reform. Other radicals took it as a further indication that what one of them calls ``a more or less open political struggle'' was taking place within the leadership.

The struggle has see-sawed dramatically in recent months. A period of relative quiescence on the part of more-radical reformers was broken at the beginning of this month by the appearance of Shatrov's play and several strongly worded articles by academics who have been prominent in the calls for change.

Then on Jan. 6 a town named in honor of former Leonid Brezhnev (party leader from 1964 to 1982) reverted to its former name. (Supporters of far-reaching change have attacked the Brezhnev era.)

And on Jan. 12, the Soviet news media carried the text of a Gorbachev talk with senior media officials. During his talk, the Soviet leader noted that the party's view on history laid out last November should be the basis for a ``deepening'' and ``rethinking'' of the past.

Shatrov said recently that he expects the play to be staged here before next June's Communist Party conference.