OpenAI’s board sacked Altman on Friday after concerns that he was underestimating the dangers of its technology.

The OpenAI staff said they would follow Altman, who said he would be starting an artificial intelligence (AI) subsidiary at Microsoft after his surprise removal from the company that created the ChatGPT chatbot, which led to the rapid rise in AI tech.

In a letter, some of OpenAI’s most senior staff members threatened to leave the company if the board was not replaced.

“The process through which you terminated Sam Altman and removed [co-founder and former president] Greg Brockman from the board has jeopardized all of this work and undermined our mission and company,” the letter, first released to the technology news outlet Wired, reads.

“Your conduct has made it clear you did not have the competence to oversee OpenAI”.

“Microsoft has assured us that there are positions for all OpenAI employees at this new subsidiary should we choose to join.”

According to reports, as many as 500 of OpenAI’s 770 employees signed the letter.

The company’s board sacked Altman on Friday after concerns that he was underestimating the dangers of its tech and leading the company away from its stated mission.

OpenAI appointed Emmett Shear, a former chief executive of Amazon’s streaming platform Twitch, as its new CEO, the third in as many days.

In a post on X announcing his appointment as interim CEO, Shear denied reports that Atlman’s sacking was due to safety concerns.

But Altman’s exit triggered the departures of other high-profile members of the company, as well as resulting in pushback from investors who asked that he be brought back.

However, OpenAI stood by its decision.

In a memo sent to employees on Sunday night, the company said, “Sam’s behavior and lack of transparency … undermined the board’s ability to effectively supervise the company,” the New York Times reported.

Microsoft CEO Satya Nadella wrote on X that Altman “will be joining Microsoft to lead a new advanced AI research team”, along with Open AI co-founder Brockman, who announced he would be leaving the company following Altman’s departure.

Nadella added that Microsoft was looking forward to working with OpenAI’s new team under Shear and that they remain “committed to our partnership with OpenAI”.

The tech giant Microsoft has invested more than $10bn in OpenAI and has rolled out the AI pioneer’s tech in its products.