(Bloomberg) -- Avast Plc shares dropped the most in more than two years after U.K. regulators surprised investors with a warning that the firm’s proposed $8.6 billion takeover by NortonLifeLock Inc. risks reducing competition for cyber security software. 

The Competition and Markets Authority will carry out an in-depth investigation unless the companies offer solutions to concerns within five working days, according to a statement Wednesday. The deal had cleared all regulatory conditions except for the U.K. approval.

“The decision is surprising,” Tempe, Arizona-based NortonLifeLock said in a separate statement, adding that it does not intend to propose remedies. The company now expects the deal to close in the second-half of the year, compared with April previously.

Avast dropped as much as 15% in London, having soared more than 25% since talks on a deal were first reported in July. The sector has also received a boost amid expectations that Russia’s invasion of Ukraine would spur an increase in demand for cyber protection software. NortonLifeLock was 7% lower in U.S. premarket trading. 

John O’Mara, an event-driven analyst at Avalon Capital Partners Limited, still expects the deal to complete, however the CMA decision came as a surprise given the transaction was cleared by every other regulator, he said in an e-mailed comment. Peel Hunt LLP analyst Oyvind Bjerke said the combination between both firms give them a “better chance to compete” against large technology companies, which is probably better for consumers.

“This transaction can only benefit consumers across the globe, including in the U.K., through increased innovation and greater consumer freedom,” NortonLifeLock said. 

(Updates NortonLifeLock price, adds analyst comments and time-line precision)

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