The Competition and Markets Authority (CMA) said in a statement that it has requested feedback from interested parties regarding the partnerships.

"Today we're inviting comments into the partnerships between Microsoft and Mistral AI, Amazon and Anthropic, and Microsoft's hiring of former employees and related arrangements with Inflection AI," said Joel Bamford, executive director of mergers at the CMA.

"We will assess, objectively and impartially, whether each of these three deals fall within UK merger rules and, if they do, whether they have any impact on competition in the UK."

Microsoft recently announced the appointment of Inflection boss Mustafa Suleyman as head of a newly created consumer AI unit.

Inflection is a rival to OpenAI and Anthropic in building the models that deliver ChatGPT-style AI.

The UK move comes after regulators in the United States and European Union launched similar examinations into such tie-ups.

Amazon on Wednesday voiced surprise at the action being taken by the UK watchdog.

"It's unprecedented for the CMA to review a collaboration of this type," it said in a statement.

"We're confident that the facts speak for themselves, and hope the CMA agrees to resolve this quickly."