US group Nvidia Corp's planned $40 billion purchase of British chip designer ARM is likely to be subject to a lengthy inquiry after a UK regulator found the deal would hit competition and could weaken rivals.
Britain's Competition and Market's Authority said the takeover could lead to "significant competition concerns".
It said Nvidia had offered remedies to lessen the impact but the CMA did not believe they would alleviate its concerns.
"The CMA found that the merger should be progressed to an in-depth Phase 2 investigation on competition grounds," it said.