''He died with the hammer in his hand." The words of "The Ballad of John Henry", which I haven't heard since childhood, have just come back to me. The legendary 19th-century railroad builder raced against the newfangled steam hammer that threatened to supplant his labour. He won, but it cost him his life. In Switch Triptych, Adriano Shaplin's anti-heroine Lucille is a switchboard operator who tries desperately to handle more calls than the automatic switching machine that Bell Atlantic management has introduced.

Set in New York in 1919, the play follows three female operators and their two male managers in the hours before automation renders the women redundant. June, the union representative, arrives to urge solidarity and to organise a walkout, but to no avail.

Shaplin's message is not as sentimental as it first appears. The women he creates are hardly symbols of working-class nobility. Lucille drinks champagne and every other concoction known to womankind and descends into alcoholism. Her rule is no drinks before 6pm, so 7.40am is fine. She has reduced her fellow operators to servitude, and under her tutelage a younger operator, Philippa (played by Sarah Sanford), sprawls inebriated on the floor of the exchange.

Lucille is a New York celebrity by virtue of the influence she wields. She runs a racket which is a kind of variant on the Yellow Pages. Callers looking for a plumber or undertaker are connected with businesses that pay Lucille bribes. Until she starts frenetically tugging at the wires in the showdown with the new machine, the only call she has condescended to handle was a corrupt client haggling over her rates.

Even if Lucille and her platoon were less selfish, June's speeches would ring hollow. The union has nothing to offer but resistance to technological advance. The tide of progress is unstoppable (a point that Peter Mandelson, with his import quotas, should note).

June's speeches are based on a text by Norman Mailer, who wrote in The Armies of the Night: "Nothing is more intrinsically opposed to technology than the bleeding heart of Christ." June asks: "What kind of Christian worships at the feet of a corporation?" But Shaplin complicates the message because he shows us the greed only of the workers, not the company. Lucille is not worried about losing her job. A girl like that will never go without. But the new switchboard will end her racket. Nor does Shaplin produce stereotypical managers. Truman and Andrew (Paul Schnabel and Drew Friedman) are useless, humourless and mildly lascivious. Keeping off drink and playing the horses are more on their minds than the health of Bell Atlantic. They are poor capitalist lackeys who allow the workforce to drink away the shift.

Switch Triptych is written like muscular poetry. It is rich in rhythm, repetition and alliteration. But, under the direction of Shaplin, the managers speak like automata, delivering lines in a staccato manner that robs them of meaning. As the play advances, all the characters begin to yell, approaching hysteria. During much of the second act, electronic gongs sound loudly and repetitively, marking the rhythm of the text, and providing the crescendo towards the duel between woman and machine. The din drives the audience almost to insanity. There are more empty seats in the auditorium at the end than at the start.

Stephanie Viola dominates the performance as Lucille. This tyrant of the telephone exchange oozes contempt. She is a starlet to whom men and women pay homage. Her earnings and status have liberated her from a drunken husband, freeing her to booze and flirt. As her monologues meander around matters of religion, they border on both obscenity and blasphemy. Did Shaplin perhaps draw inspiration from Madonna?

Lucille lives in a world of fantasy and alcohol-induced tableaux, largely indifferent to the real world and other people, except that, as an Italian American, she disdains the Irish and loathes the Protestants (both points of historic interest).

It seemed to me jarring to write June as an Englishwoman. I understand the strength of English Christian socialism in the early 20th century, but she seems an unlikely figure to rally the workers. The jokes around her Englishness are not bad ("You from Britain or just England?"), but the character made little sense.

Since 1999, the Riot Group theatre company has won four Scotsman Fringe First awards at the Edinburgh Festival with Shaplin plays. On this occasion, it seems to have missed the mark. When I saw the play in London, the curtain fell to lukewarm applause. As a text, Switch Triptych repays reading. As a stage play, it fails.

Booking (0870 429 6883) until 8 October