"The theater is my first love . . . and hate," declares playwright Kathleen Betsko. As of late, the ardent side of the relationship has been having its way, due in large part to a renewed interest in Betsko's play "Johnny Bull," which like a jilted lover parted ways with its audience following its premiere at the Yale Repertory Theatre in 1982.

But, at last, reconciliation. The play recently opened here at Horizons Theatre, where it runs through May 18, and will be staged next fall in New York at Joe Papp's Public Theater.

"It's having this wonderful resurrection," the British-born Betsko says of "Johnny Bull," the saga of a 19-year-old English girl who goes to the States with her GI husband, expecting to find the America of Doris Day movies. Instead, she finds a depressed Pennsylvania coal-mining town -- a scenario not dissimilar to Betsko's own introduction to this country.

Betsko credits Lloyd Richards, artistic director of the Yale Repertory Theatre, for her perseverance at playwriting. "He keeps an eye on me when I'm straying too far from the theater ," she says, noting that the superior pay for television writing is always a temptation. (Her TV credits include an adaptation of "Johnny Bull," starring Colleen Dewhurst and Jason Robards, which will be shown May 19 on ABC.) "He gives me an opportunity to be in that ring and slug it out once in a while."

The boxing allegory is an appropriate one for Betsko, who is waging a fight on behalf of all women playwrights for equality in the theater. "Male critics have difficulty identifying with a central female character as a metaphor for their own experience," she says. "Women playwrights are not allowed the luxury of metaphor: A kitchen sink in a female play is just a sink, but in a male play it could be the British Empire."

Critics, argues Betsko, critique plays with a different vocabulary, depending on the gender of the playwright. The anger of a male playwright, she says, is described as "raw, vital or antiestablishment," whereas that of a female playwright is called "bitter, with the connotation of being disgruntled."

Betsko and novelist Rachel Koenig recently completed a three-year collaboration on "Interviews With Contemporary Women Playwrights," a book to be published by William Morrow this fall. While conducting their preliminary research, Betsko says, she and Koenig "found more on women pirates than on women playwrights. Even the feminist scholars had neglected them ."

The objective of the book -- which includes interviews with 30 women playwrights, including Marsha Norman, Beth Henley, Emily Mann and Caryl Churchill -- is to "try to stop our history from slipping away," says Betsko, adding that 150 hours of tape from the interview sessions is being donated to the Women in Literature Archives at Smith College. She is planning an "international gathering of women playwrights" to be held sometime next year or in 1988.

"I am an outspoken feminist," says Betsko, "but every time I have an angry woman on stage, I'm not making a feminist declaration. It might just be an angry woman on stage."

Betsko, who has been through stints as a factory worker, delivery woman and welfare recipient, is equally concerned with the plight of the working class. "Poor people are severely misunderstood and not well portrayed on stage," she says. "If I have a goal at all, it's to bring my work to the people that it's about. Nothing would give me more pleasure than to have 'Johnny Bull' done in front of unemployed coal-mining families."

"Johnny Bull" is the second play of a trilogy that begins with "Beggar's Choice," which was produced by National Public Radio's "Earplay" in 1980, and ends with "Stitchers and Starlight Talkers," which was staged last January at the Yale Repertory Theatre's Winterfest of New Plays. "I would like to have a theater trust me enough to put the work together so that we could see this trilogy," says Betsko, conceding that "it would require some work."

She says she is now writing a play "about California's homeless punk teen-agers," a subject that shares some elements of her own experience. "I grew up as a homeless child," explains Betsko, who at the age of 1 was evacuated from Coventry, England, when the bombs began falling during World War II and she remained separated from her mother for the next 10 years.

Later this month Betsko will return to Coventry, where "Johnny Bull" will have its British premiere at the Belgrade Theatre. "It's a culmination of a dream for me to be able to go home as an artist," she says. "The last time my name was in the English papers I was in reform school."

Why?

"I was incorrigible, apparently," she replies. Then she adds gleefully, "I still am, but I'm too old for reform school now."