Harold Pinter's first new play in four years lasts 17 minutes. At a ticket price which works out to 30 cents a minute, it's Britain's most expensive play.

"Mountain Language," presented in the early evenings by the National Theater, consists of four grim, brutal vignettes.Despite its brevity it uses top-flight British actors - Michael Gambon, Eileen Atkins, Miranda Richardson. Pinter, as his own director, employs a cast of 12, a revolving three-area set, a full and elaborate production.

Yet it's over almost before you settle in your seat.

"It is like a few terrible photographs with captions," one critic wrote. And it is true that for much of its 17 minutes its characters are frozen in Pinter's trademark motionless pauses.

Some reviewers found it a miniature marvel. Others agreed with the critic who complained: "The piece isn't worth tuppence." Most observers seem puzzled over where Pinter - at 58 one of Britain's most famous playwrights - is heading.

He hasn't written a full-length play for 10 years. His last play, "One for the Road" in 1984, lasted only 45 minutes - and like "Mountain Language" was about torture.

The new work grew from Pinter's trip through Turkey with American playwright Arthur Miller. Pinter said it was "the first time I'd ever been in a place where I actually met people who had been tortured." But he issued a public denial that the play depicts Turkey's treatment of its Kurdish minority.

So on stage, two sadistic army officers in a nameless country torment eight women waiting outside a prison. One woman has been savagely bitten by a dog. The officers' chief concern, however, is to order the women not to speak their "mountain language" - the language itself is outlawed.

Two women get into the prison to see their brutalized men. One reacts by descending to the torturers' gutter language. The other is shocked into a speechless, motionless trance.

End of play.

Out of this and his previous torture play, some pundits debated whether Pinter has "become very political." A television documentary coinciding with the new play surprised Pinter himself by extracting heavily charged political content from his earlier plays.

"I suddenly realized that I've been leading a quite naked life in my work," he said afterward. "I've been employing these elements for years without knowing it."

Lately, however, his politics have become more openly public and highly vocal. A recent profile said he erupts in "notorious social tirades" about "the savageries and hypocrisies of the world."

"He has had plenty to say about Nicaragua, the Kurds, about Reagan and Thatcher, about censorship and writers in prison," it said. Pinter is donating some "Mountain Language" royalties to the Writers in Prison fund of the international writers' group PEN.

Yet in recent years, Pinter has put on stage only one of his many, deeply held political concerns - his abomination of torture. And he has presented that subject only in two brevities.

He has been writing screenplays - at least 17 of them, including "The French Lieutenant's Woman" and four from his own plays, "The Caretaker" and "Betrayal" among them. He's also a notable director of other writers' plays.

As a playwright, he has a towering reputation as the inventor of a theatrical style, the author of plays of menace, allusive and indirect, with a language of expressive pauses.

In its use of these elements, "Mountain Language" is characteristic Pinter. But it is a mere sketch, although capably acted and expensively produced, and as thin as it is brief.

It remains in the National Theater's repertory for an indefinite period, usually playing before performances of Ben Jonson's "Bartholomew Fair."