Probes by the European Commission into illegal cartels, price-fixing and other anti-competitive practices more than tripled last year, according to Thomson Reuters' legal business.
The rise in investigations comes as the EU ramps up its efforts to promote fair trading across the Single Market, the firm said.
Antitrust investigations opened by the Commission increased by 253 per cent over the last 12 months to 473, and most related to cartels and price fixing, market monopolies and abuse of market dominance.
“The European Commission is coming down hard on companies looking to gain an illegal and unfair advantage,” said Karen Williams, head of practical law competition at Thomson Reuters.
“The growth of e-commerce has been a driver of the rising number of investigations in recent months but this is just part of the European Commission’s current focus, as companies across the European economy continue to jostle for position and profits.”
The focus on e-commerce follows the Commission's sector inquiry launched in 2015, which was published this May.
It highlighted concerns around “geo-blocking”, where a company prevents consumers from accessing its products based on their nationality or place of residence, and most often takes the form of companies refusing to deliver goods to customers in countries beyond the business's base.
The Commission launched 90 investigations in February, including its first full-scale probes into e-commerce companies including consumer electronics manufacturers, video games publishers and holiday tour operators.
Today, the Commission found Luxembourg had given Amazon €250m worth of illegal tax benefits and ordered the online giant to pay the sum back.
Outside e-commerce, antitrust cases have also targeted sectors including transport, automotive and financial services.
A new whistleblowing tool, introduced by the Commission in March, is set to increase the number of investigations further.
To date, most cartels have been identified through a programme which allows businesses to report their own involvement in return for a fine reduction. But now, individuals can use an encrypted messaging system which allows them to retain anonymity.