Johann Hari and his publisher Bloomsbury have apologised after the author wrongly claimed in his latest book that Observer restaurant critic Jay Rayner had taken the diabetes drug Ozempic.

In Magic Pill, Hari claimed that Rayner said Ozempic “robbed him of his pleasure in food so severely that even in great restaurants in Paris, he couldn’t find any joy”. In an X post on Sunday, Rayner said that Hari’s claim was “complete and utter bollocks” and that he has “never used Ozempic or anything similar”, linking to a column he wrote in which he had explained why he would never take the drugs. He said that he was “mystified” as to why Bloomsbury “did not go through the text with a fine tooth comb”.

Hari then apologised to Rayner, and said that he had confused Rayner’s article with a different Guardian article by Leila Latif about “losing pleasure in food”. Latif said in response that she has never been on semaglutide, the drug sold under the brand name Wegovy for weight loss and Ozempic for diabetes. “You are misrepresenting a very personal piece of writing,” she added. In the article, Latif wrote about her experience of losing her appetite after starting a new medication for a longstanding health condition. Though this medication was not semaglutide, the article’s original subheading mistakenly said that it was. This was amended and an explanatory footnote was added to the article on the same day it was published.

“We sincerely apologise for any distress caused,” said Bloomsbury on X in response to Rayner’s post. “This is an unfortunate mistake and we will correct it across all formats. We confirm there was a fact checking process in place for the book. The error occurred when an article was wrongly attributed to you.”

“I’m really sorry that I made this mistake in this paragraph of my book. I apologise to the journalists involved, and the distress it has caused them”, Hari told the Guardian.

He added that he was “gutted” to have made this error, and that it “got through the fact-checking processes that I put in place to spot any mistakes I might make. I take full responsibility for it.”

Latif and Rayner are in email contact with Bloomsbury about the situation. Rayner said that he is “pleased” that Bloomsbury has agreed to correct the text, and in the UK put errata slips in existing copies.

Latif said that Hari has not yet apologised to her. “For any person, but particularly if you’re a woman, and a woman of colour, discussions around your body feel very, very difficult,” she said. It is “massively inappropriate for him to be discussing people’s relationships with their weight”.

A spokesperson from Bloomsbury told the Guardian that the publisher is “in the process of correcting the mistake.”

“Bloomsbury is very proud to publish Johann Hari”, they added. “We have seen first hand how incredibly hard he has worked on his four books, which have deservedly had an extraordinary impact all over the world.”

Rayner was made aware of the incorrect claim via a Google Alert for his name – which he said he has turned on “specifically for this sort of thing” – because it appeared on the transcripts of two podcasts Hari had spoken on, including Steven Bartlett’s Diary of a CEO.

Hari has been accused of fabrication in the past, and he has admitted to plagiarism, which led him to be suspended from the Independent in 2011. “I did two things that were completely wrong. One is that when I interviewed people I often presented things that had been said to other journalists or had been written in books as if they had been said to me, which was not truthful,” he told the Guardian in 2018. “The second is that I edited Wikipedia entries regarding other people under a pseudonym and, sometimes, in very nasty ways”.