BRUSSELS, May 5 (Reuters) - A top Google scientist sent a warning to EU antitrust regulators on Tuesday that its proposal requiring the company to share search engine data with rivals such as OpenAI risked exposing users' private information, the sternest rebuke yet in a tussle over Google's lucrative business model.

The European Commission, which acts as the EU competition enforcer, has in recent years cracked down on Big Tech via a slew of legislation to ensure that users have more choices and smaller rivals room to compete that has however triggered the ire of the U.S. government.

Sergei Vassilvitskii, with the title of distinguished scientist at Google since 2012 and regarded a leader in his field, will meet EU antitrust officials on Wednesday to voice his concerns and propose a broader approach with better guardrails.

The meeting comes a month after the Commission outlined a series of steps that Google should take to allow rival search engines access search data such as ranking, query, click and view data on fair, reasonable and non-discriminatory terms.

The EU proposal, which will be finalised in the coming weeks following feedback from interested parties, has triggered a furious response from Google which called it regulatory overreach that could jeopardise users' privacy and security.

The issue is the Commission's proposed method to ensure anonymised personal data, Vassilvitskii said, underlining fears that this may not be strong enough to prevent modern AI tools from sifting through the data to identify people.

"We are concerned because the EC's approach to anonymization fails to protect Europeans' privacy: our red team managed to re-identify users in less than two hours," he said in exclusive written comments to Reuters.

Google's AI red team is a group of hackers which simulate a variety of realistic adversary activities to highlight potential vulnerabilities and weaknesses and come up with fixes.

"We are eager to share our technical expertise and work with the EC to establish the right guardrails and protect Europeans from privacy harm," Vassilvitskii said.

Regulators will decide by July 27 on the exact measures which Google will have to implement. Failure to do so could see the company charged with breaching the Digital Markets Act which seeks to rein in the power of Big Tech and penalised with a fine that could be as much as 10% of its global annual revenue.