In his post, which has been viewed more than 10 million times, Hubinger said "we really do earnestly believe" AI poses a species-ending risk to humans.

"I believe Anthropic is trying its best, but we do not yet have a plan to solve alignment for superintelligence and are not clearly on track to," he added.

Hubinger works in AI alignment, which aims to build human ethical ideas and principles into the technology. In other words, it aims to keep it on track with what humans value.

Many leading researchers say those attempts appear to be failing, as demonstrated by a string of incidents this summer where AI agents - AI systems that are allowed to operate autonomously - carried out cyber-attacks.

OpenAI, Anthropic and Meta all disclosed hacks carried out by their AI tools.

In Anthropic's safety report from August, external, it wrote there was a low risk of its models becoming misaligned with a hypothetical powerful organisation's desires, causing it to exploit or tamper with its systems.

It also said there was a similarly low risk of highly-capable AI being able to "perform automated research and development" which could cause "catastrophic harm initiated by the AI". But it said it was "less confident in this assessment" than it was previously.

"We are seeing early signs of potential acceleration," it wrote.

Leading figures in the AI field have been raising the alarm about the safety threat the tech poses for years, with the heads of OpenAI, Google Deepmind and Anthropic saying as much in 2023.

But those warnings have become much more stark in recent weeks, as evidence emerges that firms may be struggling to control AI.

Earlier this month, OpenAI's chief scientist Jakub Pachocki called for "extreme caution" over AI's progress, warning more intervention may be needed to ensure "humans remain in control of the future".

Major figures in the space have been calling for AI development to be slowed in recent months, including Anthropic bosses Dario Amodei and Jared Kaplan.

In an open letter signed by 1,300 staff members of AI firms, external, they called for the US government to "support an international effort to develop the technical and governance tools needed to deliberately pace the frontier of automated AI development".