LONDON (Reuters) -Britain dropped its probe into Microsoft's ( MSFT ) partnership with ChatGPT maker OpenAI on Wednesday, saying the software giant did not have the level of control over the AI company that would warrant further investigation.

The partnership came under antitrust scrutiny in Britain and the U.S. last year following the startup's boardroom battle that led to the exit and return of CEO Sam Altman.

Britain's Competition and Markets Authority (CMA) said although Microsoft ( MSFT ) did acquire material influence over OpenAI in 2019, it had not since gained de facto control and therefore it did not qualify for review under the UK's merger control regime.

A Microsoft ( MSFT ) spokesperson said the partnership with OpenAI and its continued evolution "promote competition, innovation, and responsible AI development".

"We welcome the CMA's conclusion, after careful and prudent consideration of the commercial realities, to close its investigation," the spokesperson said.