Apple Chief Executive Tim Cook on Wednesday said customer data was being "weaponised with military efficiency" by companies to increase profit and called for a federal privacy law in the United States.
But Facebook CEO Mark Zuckerberg defended his company's ad-based business model said users were aware of a trade-off for free services.
Cook, speaking at the International Conference of Data Protection and Privacy Commissioners, said Apple would support a US privacy law and also touted the iPhone maker's commitment to protect users' data and privacy.
Apple, which designs many of its products so that it cannot see users' data, has largely avoided the data privacy scandals that have enmeshed its rivals Google and Facebook this year.
"The desire to put profits over privacy is nothing new," Cook told a packed audience of privacy regulators, corporate executives and other participants.
Issues over how data is used and how consumers can protect their personal information are under the spotlight after big breaches of data privacy involving millions of internet and social media users in Europe and the United States.
Cook in his speech cited former US Supreme Court Justice Louis Brandeis who in a Harvard Law Review article in 1890 warned that gossip was no longer the resource of the idle and the vicious but had become a trade.
"Today that trade has exploded into a data industrial complex. Our own information, from the everyday to the deeply personal, is being weaponised against us with military efficiency," Cook said.
"These scraps of data ... each one harmless enough on its own ... are carefully assembled, synthesised, traded, and sold," Cook said.
"We shouldn't sugarcoat the consequences. This is surveillance. And these stockpiles of personal data serve only to enrich the companies that collect them," he said.
FACEBOOK'S AD-BASED MODEL
Zuckerberg, speaking via video message, said Facebook users were aware of the trade-off between a free service and advertisements.
"Instead of charging people, we charge advertisers to show ads. People consistently tell us that they want a free service and that if they going to see ads to get it, then they want those ads to be relevant," he said.
Facebook was investing heavily in both security and privacy even as this impacts on its profitability, Zuckerberg said.
Google Chief Executive Sundar Pichai welcomed the global focus on privacy, saying that the company was doing its part by taking measures to allow users more control over their data.
"User trust is the foundation for everything we do, and privacy and security are fundamental tenets of that," he said by video message. "We've been working for years to provide more transparency and control for our users, and we appreciate the input and partnership from data protection authorities."
Cook also warned about governments abusing users' data and their trust, a concern for many with elections coming up in several countries.
"Rogue actors and even governments have taken advantage of user trust to deepen divisions, incite violence, and even undermine our shared sense of what is true and what is false."
Cook said Apple fully backed a federal privacy law in the United States, something Europe has already introduced via its General Data Protection Regulation."Users should always know what data is being collected and what it is being collected for," he said. "This is the only way to empower users to decide what collection is legitimate and what isn’t. Anything less is a sham."