A New Testament scholar claims to have found evidence suggesting that the Gospel of Jesus's Wife is a modern forgery.

Professor Francis Watson, of Durham University, says the papyrus fragment, which caused a worldwide sensation when it appeared earlier this week because it appeared to refer to Jesus's wife, is a patchwork of texts from the genuine Coptic-language Gospel of Thomas, which have been copied and reassembled out of order to make a suggestive new whole.

In a paper published online, Watson argues that all of the sentence fragments found on the papyrus fragment have been copied, sometimes with small alterations, from printed editions of the Gospel of Thomas.

The discovery has already sparked fierce debate among academics, but Watson believes his new research may prove conclusive.

"I think it is more or less indisputable that I have shown how the thing was composed," he said. "I would be very surprised if it were not a modern forgery, although it is possible that it was composed in this way in the fourth century."

His paper claims the work was assembled by someone who was not a native speaker of Coptic, which is a polite way of saying that it is modern.

He does not directly criticise Professor Karen King, of Harvard, who presented the fragment at a conference in Rome this week. He says she has done a very good job of presenting the evidence and images of the disputed fragment. He believes the papyrus itself may well date from the fourth century, but the words, he says, clearly show the influence of modern printed books.

In particular, there is a line break in the middle of one word that appears to have been lifted directly from modern editions of the Gospel of Thomas, a genuine Gnostic or early Christian text.

It is common for words to be broken in the middle in ancient scripts, like Coptic, which were written without hyphens, he says. But it is most uncommon for the same break to appear in the same work in two different manuscripts.

There has been no response as yet from King, who is believed to be still travelling after the Rome conference.

Martin believes this is a forgery comparable with a papyrus fragment that caused a scandal in the 1970s by being presented as a variant of the Gospel According to Mark, in which Jesus spent the night with naked youths.

"It's the same sort of technique – patchwork technique. This is particularly striking in the Jesus's Wife text, because it has little bits that are legible and they don't connect very well," says Martin.

There has long been speculation that Jesus might have married – most notably in recent years when it became a key part of the plot in Dan Brown's The Da Vinci Code.