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Big tech companies face hefty fines in Britain and the European Union if they treat rivals unfairly or fail to protect users on their platforms, in proposed regulations unveiled Tuesday by officials in London and Brussels.

The EU outlined its long-awaited sweeping overhaul of digital regulations while the British government released its own plans to step up policing of harmful material online, signalling the next phase of technology regulation in Europe.

Both sets of proposals include specific measures aimed at the biggest tech companies. The EU wants to set new rules for “digital gatekeepers” to prevent them from imposing unfair conditions, such as blocking businesses from accessing their own data or locking consumers into services and limiting their options for switching.

The rules, known as the Digital Markets Act, set out criteria for defining companies as gatekeepers and allows for fines of up to 10 per cent of annual global revenue.

Another part of the EU plan, the Digital Services Act, updates the bloc’s 20-year-old rules on e-commerce by making online platforms take more responsibility for their goods and services. That can include weeding out shady traders and swiftly taking down illegal content such as hate speech, though in a bid to balance free speech requirements, users will be given the chance to complain. Violations risk fines of up to 6 per cent of annual turnover.

In Britain, social media and other internet companies face big fines if they don’t remove and limit the spread of harmful material such as child sexual abuse or terrorist content and protect users on their platforms.