Mumsnet has denied using AI to produce content after detailed instructions to help an AI model write one of its popular “am I being unreasonable” (AIBU) posts appeared on a Mumsnet message board.

Users of the long-established forum, which is known for its frank discussions of family tensions, were vexed when the AI prompt appeared in response to a user seeking advice about a family dilemma involving a neurodivergent uncle and a sick child.

The user, called AmIAComplete, had asked for “a sanity check” from other users after an awkward social interaction with their brother’s family but was met with a prompt titled AIBU Response Schema v.1.0.

It instructed an AI to write an “interpersonal reasonableness” post and “give a clear, forum-style ruling plus brief actionable advice”. It included definitions of common Mumsnet abbreviations including AIBU, ND (neurodivergent) and DD (dear daughter).

The prompt said: “do not diagnose anyone; do not demean ND people; do not imply a sick child owes social performance” and said “prioritize compassion, boundaries, and de-escalation”.

Site users called the emergence of the prompt “really creepy”, “crazy” and “so disappointing” and it fed speculation about Mumsnet’s use of AI, with one user saying: “We might as well just go and do something else then.”

Mumsnet was founded in 2000. It faced a 19% drop in its monthly unique user numbers in 2025 to 6.1 million and the number of posts fell by 600,000. It said in its latest annual report that it was “embedding AI tools to improve productivity and enhance the user experience”.

Recent research, published in Nature, has shown that AI assistance in social media risks creating “semantic garbage” and is seen by users as less informative, “robotic” and “generic”.

Soon after the prompt emerged, Mumsnet denied that it used AI to write threads and said it had come from a tool to suggest thread titles which uses an OpenAI model. But users refused to accept this explanation and some copied the prompt into an AI and found it generated a full post.

“We are not idiots,” said one user, MrsBennetsPoorNervesAreBack. “Please can you give us a transparent explanation?”

Mumsnet then said the prompt did not come from them and suggested it had somehow transferred from AmIAComplete’s computer. Again users were unconvinced and speculated the prompt must have leaked from Mumsnet’s internal system.

Mumsnet’s founder, Justine Roberts, joined the thread and confirmed the prompt had come from its system, which sends users’ drafts to OpenAI, which is meant to suggest a title, although this time it sent a prompt for a whole reply. She said it “looks like an error on their side” and said: “We don’t use AI to write threads or replies on Mumsnet.”

This explanation also failed to appease users, who said they were being “fobbed off”.

“Why would OpenAI compel itself to do/try to do something so specific if it’s never been asked to do that before from your side?” said one. “It’s like it’s appeared in the wrong place. Rather than just sprung out of thin air.”

“I just don’t know anymore what’s real and what isn’t sometimes!” they said.

Roberts told the Guardian: “I understand why it looked like it had ‘appeared in the wrong place’. But nothing in our systems asks for, stores or uses anything like it.”

“Mumsnet works because the people on it are real,” Roberts said. “Members trust that the advice they get comes from other parents, not a machine … This episode was a useful reminder of two things. First, these systems are less predictable than the people selling them like to suggest. Second, users are understandably highly concerned that Mumsnet remains written by humans.”