“The United States is fundamental and we will always maintain a privileged connection with it but when it comes to... policy decisions we’re a sovereign state,” he told a press conference in London after a NATO summit.

“We can exchange opinions and evaluations, but then it’s the sovereign state that decides.”

Italy’s 2020 budget introduces a 3 per cent levy on revenue from internet transactions for digital companies with sales of at least €750 million, at least €5.5 million of which are made in Italy.

The new tax is expected to bring in some €600 million in revenue for Italy every year.

US President Donald Trump’s administration has repeatedly argued the levy unfairly targets US tech giants like Amazon, Facebook, Apple and Google.

Britain and France also plan to impose digital tariffs affecting US firms.

The US on Monday warned Italy not to go ahead with a planned tax, and threatened to impose tariffs of up to 100 per cent on France for bringing in a similar law.

French produce, including Champagne and cheeses, could be targeted as soon as mid-January after a report from the US Trade Representative’s office found the country’s incoming 3 per cent tax to be unfair.

“[The decision] sends a clear signal that the United States will take action against digital tax regimes that discriminate or otherwise impose undue burdens on US companies,” US Trade Representative Robert Lighthizer said in a statement.

The European Commission claims that Apple had paid an effective corporate tax rate of just 0.005 per cent on its European profits in 2014 – equivalent to just €50 on every €1 million.