The following correction was printed in the Guardian's Corrections and clarifications column, Thursday April 12 2007

In the article below, the knighthood conferred by us on Percy Shelley was a mistake. Shelley was the eldest son of a baronet but died before his father. This has been corrected.

The latest sensation to galvanise the torpid lit-hist-crit establishment is the "discovery" by market research analyst John Lauritsen that Mary Shelley did not write Frankenstein; Or, the Modern Prometheus (to give the novel its full title). John Lauritsen, it should be remembered, is the gay rights activist who has been fighting a lonely battle against the commonly accepted notion that HIV is what causes Aids. It is his belief that the real cause of the occurrence of Kaposi's sarcoma among gay men is not a retrovirus, but their frequent recourse to amyl nitrite inhalants (poppers). Sadly for Mr Lauritsen, nobody has been paying attention to his howling in the wilderness on these topics and so he has been forced to search out another dead horse and give it a good flogging instead. Curiously, in this instance, he appears to be having some success. The media are taking his arguments seriously. His book, The Man Who Wrote Frankenstein, is not out in the US till next month, but already the chattering classes are chattering about it.

The logic goes something like this: Frankenstein is a masterpiece; masterpieces are not written by self-educated girls and therefore Frankenstein cannot have been written by Mary Shelley. If Frankenstein is not a masterpiece, the thesis collapses. Though millions of people educated in the US have been made to study and write essays about Frankenstein, it is not a good, let alone a great novel and hardly merits the attention it has been given, notwithstanding the historic fact that its theme has inspired more than 50 (mostly bad) films.

Literature courses in the US are oddly skewed towards novels because few undergraduates are required to read any poetry. If Lauritsen had read a sufficient quantity of poetry, he would know better than to state that the monster's famous statement that he will "glut the maw of death" by killing all those whom Frankenstein loves, is pure Shelley, because it is, of course, pure Milton (Paradise Lost, Book 10).

In 1818 when Frankenstein was first published anonymously, with a preface by Percy Bysshe Shelley, most reviewers assumed he had written it himself, except for those who suspected that it was written by someone even less experienced than he, perhaps the daughter of a famous novelist, as Mary Shelley was. Marks of inexperience can be found on every page. There are three narrators: Thomas Walton, Victor Frankenstein and the monster himself. The three of them, including the inarticulate monster, speak in paragraphs, with the same tendency to proliferating parallel clauses and phrases and the occasional theatrical ejaculation. The climactic ponts of the action remain undescribed, usually because the abnormally sensitive male narrator has fainted or fled or become deathly sick. The narrative has more loose ends than a grass skirt. The creature made by Frankenstein out of decaying spare parts knows the function of clothes and finds some to fit his 8ft frame and pops them on before he vanishes from the laboratory at more than human speed. The author only grasps the improbability of this sequence of events in the third volume, but can do nothing to resolve it. The account of the monster's education, from speechless to fully literate in a year, would be risible if it were not for its resemblance to Mary's scrappy education.

The greatest improbability in Mary's story is the one she is least able to confront. A man who dared to manufacture a human being should surely have been prepared to trash it and start again but, instead of stifling his hideous creature at birth, Frankenstein runs away and wanders round Ingolstadt all night. Throughout the novel he remains incapable of confronting the task of killing the creature he made or even realising it is his duty to do so. He is more like the mother of a monstrous child than like the maker of a fake human.

Indeed, the monster is made as human as any other character; his depravity is the consequence of his miserable existence and his existence is Frankenstein's fault.

The driving impulse of this incoherent tale is a nameless female dread, the dread of gestating a monster. Monsters are not simply grossly deformed foetuses. Every mass murderer, every serial killer, the most sadistic paedophile has a mother, who cannot disown him. Percy was capable perhaps of imagining such a nightmare, but it is the novel's blindness to its underlying theme that provides the strongest evidence that the spinner of the tale is a woman. It is not until the end of the novel that the monster can describe himself as an abortion. If women's attraction to the gothic genre is explained by the opportunity it offers for the embodiment of the amoral female subconscious, Frankenstein is the ultimate expression of the female gothic.

What drives Lauritsen is his loathing of the people he calls radical feminists, whom he sees as dominating the literary academy, and drowning out the voice of gay activism in literature. This is an odd interpretation of the fact that women's studies is now gender studies and that queer theory is on every syllabus, but some people are never satisfied. Lauritsen believes that the true theme of Frankenstein is love between men, and that when Percy wrote it he was encoding his own version of the love that dared not speak its name. What Lauritsen makes of Shelley's poems to Mary one can hardly imagine. He probably thinks Mary wrote them.