Big tech companies will face hefty fines in the European Union under proposed new regulations if they treat rivals unfairly or fail to protect users on their platforms.

The EU outlined its long-awaited sweeping overhaul of digital regulations on Tuesday at the same time as the UK Government released its own plans to step up policing of harmful material online.

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% 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% of annual turnover.

Meanwhile, the Irish Data Privacy Commission has issued Twitter with a 450,000 euro (£404,000) fine for a security breach.

It is the first punishment for a big US tech company since the EU’s strict privacy rules, known as General Data Protection Regulation, took effect in 2018.