Microsoft's (MSFT) partnership with OpenAI does not qualify for an investigation under UK merger rules, the country's antitrust regulator said Wednesday.

In December 2023, the UK Competition and Markets Authority said it was considering whether the technology giant's partnership with the parent of artificial intelligence chatbot ChatGPT constituted a potential merger situation and, if so, whether such a situation would impact competition in Britain.

"The CMA does not believe that Microsoft currently controls OpenAI's commercial policy, and instead exerts a high level of material influence over that policy," the regulator said Wednesday. "In other words, there is no change of control giving rise to a relevant merger situation."

Shares of Microsoft climbed 2.9% in Wednesday afternoon trade.

The investigation has been "complex," with several aspects of the partnership evolving over the duration of the review, the regulator said.

"There is no 'bright line' between factors which might give rise to material influence and those giving rise to de facto control," according to the CMA. "This has required the CMA to carefully consider the commercial realities of the relationship between the parties ..., not just the formal terms of the arrangement."

Microsoft and OpenAI, which struck a partnership in 2019, said they welcome the CMA's decision.

"Our OpenAI partnership and its continued evolution promote competition, innovation, and responsible AI development," a Microsoft spokesperson told MT Newswires in an e-mailed statement.

"OpenAI operates in a highly competitive and rapidly evolving industry, and we are focused on developing AI that is safe and beneficial for everyone," an OpenAI spokesperson said in a separate e-mail to MT Newswires.

The regulator's conclusion that the partnership does not lead to a relevant merger situation "does not constitute a finding that no competition concerns arise from its operation," the CMA said.