NEW YORK (AP) _ For more than four years, ''Forbidden Broadway'' has offered audiences in New York and around the country its own particular brand of malicious merriment about the sad state of the American theater.

Now a new ''summer shock'' edition is on view at Palsson's Supper Club, a cozy West Side nightspot that has been home to this satirical musical revue since January 1982.

It's a relief to report that time hasn't turned this tiny tiger of a show into a toothless old tabby. The revue, written and directed by Gerard Alessandrini, still spares no one. From Bob Fosse to Bernadette Peters to Harvey Fierstein to Lily Tomlin, Alessandrini skewers the shows and stars of recent New York theater seasons.

It works because Alessandrini has an obvious affection for Broadway, particularly the Broadway musical, and laments its decline. Picture Fosse being chided for his recent bomb,''Big Deal,'' with a number called ''Hey, Bob Fosse 3/8 3/8'' Done to the music of Cy Coleman's ''Big Spender,'' it asks one of Broadway's biggest directors how he could forget such little things such as a plot when putting together his latest show. Or Linda Ronstadt being decimated for going eyeball to eyeball with Giacomo Puccini in a pop version of ''La Boheme.'' According to Alessandrini and company, Miss Ronstadt blinked first.

The five-member cast goes along cheerfully with Alessandrini's savagery. Roxie Lucas is an exuberant comedian. A tall, angular woman reminiscent of a young Charlotte Greenwood, she dances her way through a trashing of ''Tango Argentino,'' and then becomes an overage Orphan Annie, complete with cigarette dangling from her mouth, as she waits for the arrival of ''Annie II.''

Barbara Walsh gets the big vocal assignments, including a hilarious takeoff of Barbra Streisand's recent Broadway album and Patti LuPone's lament at being typecast forever as Eva Peron.

The three men are less successful, although pianist Mark Mitchell, an Andrew Lloyd Webber look-alike, is very funny as the phenomenally popular British composer. Craig Wells and Ron Bohmer are stuck with impersonating some people who are not readily identifiable including theatrical impresario Joseph Papp, portrayed here as ''Papp the Knife,'' and George Hearn, one of the original stars of ''La Cage aux folles.''

''Forbidden Broadway'' is at its best when tweaking such dismal dinosaurs as ''Singin' in the Rain'' and its director Twyla Tharp. That much maligned stage version of the famous movie musical rates three songs in this new revue, including such aptly titled numbers as ''Spinning Down the Drain'' and ''Make 'Em Leave,'' an acerbic version of ''Make 'Em Laugh,'' Donald O'Connor's show stopper in the movie.

''Forbidden Broadway'' will appeal most to audiences familiar with the New York theater. For people who can identify Shepard (Sam), Sondheim (Stephen) and Strouse (Charles) without a Playbill, it's the best, brightest and wickedest musical revue in New York.