JK Rowling has threatened a Harry Potter fan with a lawsuit after the person posted untruths about her family in an apparent attack on the author’s transgender views.

Rowling said she would be forced to take legal action if Wizarding News, a 22-year-old Harry Potter fan site, does not remove fabricated X messages claiming she has an estranged daughter and grandchild.

“This is untrue in all respects, as I suspect they already know. Lying about my kids is a new low, even by this website’s subterranean standards,” Rowling wrote on the site formerly known as Twitter.

“Your vendetta against me is causing collateral damage to innocent people. If legal action is the only way to protect them, I will take it.”

Wizarding News, which has more than 37,000 X followers, apparently posted images of the person they claimed was related to Rowling. The account said they later deleted the post.

Rowling said: “You’re painting a target on people who have no connection with me, who aren’t my relatives. You surely know what you’re doing, but persist. Hate me all you like, but your actions are having real world consequences for people I don’t even know.”

Wizarding News is a staunch critic of Rowling’s views on gender identity, describing her as a “small-minded bigot hellbent on denigrating trans people at every possible opportunity.”

Rowling has been in combative mood on X in recent weeks. Earlier this month, Rowling was reported to the police by former Big Brother star India Willoughby, who claimed that she had been repeatedly misgendered by the writer. The police did not pursue the matter.