Warren said in a statement that she would as president press for legislation to designate the big online companies with revenues of $25 billion or more as "platform utilities" barred from owning "any participants on that platform."

The Massachusetts senator said she would also appoint anti-trust enforcers "committed to reversing illegal and anti-competitive tech mergers," including acquisitions in recent years by Amazon, Facebook and Google.

"Today's big tech companies have too much power -- too much power over our economy, our society, and our democracy," she wrote in a blog post on Medium.

"They've bulldozed competition, used our private information for profit, and tilted the playing field against everyone else. And in the process, they have hurt small businesses and stifled innovation."

The proposal comes amid a growing "techlash" movement in the United States against the firms, which have grown to become the world's most valuable, amid concerns on handling of private user data and dominance of certain sectors such as online retail and internet search, and a series of antitrust investigations in Europe.

Warren specifically said she would seek to unwind Amazon's acquisition of the Whole Foods grocery chain and shoe retailer Zappos; Facebook's WhatsApp and Instagram; and Google's integration of the ad tech firm DoubleClick, internet of things maker Nest and mobile navigation application Waze.

"Unwinding these mergers will promote healthy competition in the market -- which will put pressure on big tech companies to be more responsive to user concerns, including about privacy," she wrote.

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