Britain will be “weaker” after Brexit, the European Commission President has said, insisting the European Union is “beautiful” to many people across the world.

Jean-Claude Juncker also criticised Theresa May’s bid to be a “bridge to Donald Trump”, saying: “To put it brutally, we don’t need the United Kingdom Government to organise our relations with the US.”

However, Mr Juncker backed the Prime Minister by agreeing the controversy over the rights of EU citizens – and Britons in other EU countries – will be resolved quickly.

The former Prime Minister of Luxembourg gave a combative interview to Time magazine, within days of announcing he will step down when his current term ends in 2019.

At this month’s EU summit in Malta, Ms May attempted to convince other EU leaders that her coup in becoming the first world leader to meet the US President made her a link between the two continents.

But Mr Juncker rejected that offer, adding: “In fact, according to President Obama, Britain is weaker being outside the European Union than being a member of the European Union. That is the case.”

The Commission President also rejected Mr Trump’s prediction that other countries will leave the EU after Britain, saying: “I don’t think anyone else is tempted to take the same route. That was highly unfriendly and not helpful at all.”

And he turned his fire on Ted Malloch, the US President’s reputed pick to be his ambassador to the EU, who has likened the bloc to the Soviet Union and suggested it needed “taming”.

Mr Juncker said: “If he wants to be an ambassador for the US in the European Union, he has to improve his knowledge and watch his words from time to time.”

He added: “The unity of Europe is a precondition for a better organised world and, if the European Union would fail or decompose or other members left, the US would have a more difficult role to play in the world.”

Mr Juncker also mounted a fierce defence of the EU’s record, in the face of a rise in anti-EU populists, saying: “We are not proud enough of what we have achieved.

“This was a continent of divisions, of wars, of conflicts, of divergences, differences. When I am in Asia, in Africa, people admire what we have managed to do. Europe is beautiful seen from other continents.”

The fate of EU citizens – and British expats – will be at the forefront of attempts to amend the Article 50 bill when it is debated in the House of Lords next week.

Opposition peers will attempt to force the Government to give an immediate, unilateral guarantee that the rights of three million EU citizens in the UK will be protected after Brexit.

A threatened Tory rebellion in the Commons melted away when Amber Rudd, the Home Secretary, insisted “nothing would change” without MPs’ consent.

Meanwhile, a leaked EU document warned of a backlash against the 1.2 million Britons living in the EU – because of Ms May’s failure to offer a secure future for EU nationals in the UK.

But Mr Juncker said: “I can’t imagine that we would punish European citizens living in Britain, or that we would punish British citizens living in Europe.