Innovative guests from the Royal Court; Top Girls Play by Caryl Churchill. Directed by Max Stafford-Clark.

For the New York Shakespeare Festival this is proving to be a season of British inputs and feminist outlooks. The phenomenon began with David Hare's critically applauded ''Plenty,'' starring Kate Nelligan, now transferred to the Plymouth Theater. It traces the post-World War II disillusionment and breakdown of a British woman volunteer with the French resistance. For an unaccountably eccentric touch, producer Joseph Papp next presented a mixed-up ''Hamlet,'' with Diane Venora as the Dane.

Now comes the all-British ''Top Girls,'' by Caryl Churchill, who's ''Cloud Nine'' has been running for many months Off Broadway. The opening at the Public/Newman Theater inaugurates an exchange program between the festival and London's innovative Royal Court Theater. A play by a woman about women past and present, ''Top Girls'' challenges the attention and holds on to it with a fair degree of firmness.

Miss Churchill commences her survey of women achievers with a dinner party given by top girl Marlene (Gwen Taylor) at a posh London restaurant for a quintet of notable women from legend and history.

As written and staged, the dinner party is played for realism rather than fantasy, recalling in format Steve Allen's ''Meeting of Minds'' on TV. In the manner of such occasions, there is more talking than listening as Marlene's imaginary companions eat and drink and exchange confidences. Needless to say, all of the guests have been confronted with and/or subjected to male domination. The discourse is informative, pointed, amusing, and sometimes touching.

Dissolve to ''Top Girl's Employment Agency,'' a London service specializing in jobs for women. Except for Marlene, the women in Scene 1, including the waitress (Lou Wakefield), now become interviewers or interviewees. For the most part, the job-seekers are secretaries of varying accomplishments bent on bettering themselves. The players' total transformations in looks and personalities from their appearances in the first scene is one of the nimblest theatrical achievements of the production stage by Max Stafford-Clark. (Was no woman director available?)

In her third narrative switch, Miss Churchill focuses on the love-hate relationship between Marlene and her married sister, Joyce (Miss Findlay). An intense last-scene confrontation between the sisters is familiar but believable as acted by the Misses Taylor and Findlay.

Otherwise, this first sample of an ongoing Anglo-American exchange is a theatrical oddity in which the long view of what has been happening to womankind's ''top girls'' combines with a sharp look at contemporary women achievers and a compassionate glance at the plight of an underclass underachiever who will never know the meaning of room at the top. Apart from one cheap shock effect, Miss Churchill has written a thoughtful and imaginative theater piece with several highly exploitable acting parts for a cast that knows exactly how to make the best of them.