Executives from Apple and IBM have called for more oversight on how personal data is used following the Facebook Inc breach that saw more than 50 million users’ data misused by UK consultancy Cambridge Analytica.

Speaking at the China Development Forum in Beijing over the weekend, Apple chief executive Tim Cook said “well-crafted” regulation was required, while IBM president Virginia Rometty said users should have more control over their own data.

“It’s clear to me that something, some large profound change is needed,” said Cook. “I’m personally not a big fan of regulation because sometimes regulation can have unexpected consequences to it, however I think this certain situation is so dire, and has become so large, that probably some well-crafted regulation is necessary.”

The breach has sparked debate over the responsibility of large tech firms to properly inform users of how their data is used. “If you’re going to use these technologies, you have to tell people you’re doing that, and they should never be surprised,” said IBM’s Rometty. “(We have to let) people opt in and opt out, and be clear that ownership of the data does belong to the creator,” said Rometty.

Facebook has come under intense scrutiny from users, policymakers and investors following allegations from a whistleblower that it allowed British political consultancy Cambridge Analytica to improperly use data and build voter profiles that were later used to help elect US President Donald Trump in 2016. Its chief executive Mark Zuckaberg has been called to explain at a congressional hearing how users’ data was released to the consultancy.

Yesterday, Zuckerberg apologised to Facebook users for “a breach of trust” in advertisements placed in newspapers, including The Observer in the UK and the New York Times, Washington Post and Wall Street Journal in the US. “We have a responsibility to protect your information. If we can’t, we don’t deserve it,” said the advertisement, which appeared in plain text on a white background with a tiny Facebook logo.