LONDON (BLOOMBERG) - British Foreign Secretary Boris Johnson said it's a "myth" that freedom of movement is a fundamental right for Europeans and suggested the UK may quit the region's customs union.

The UK may have to leave the bloc's customs union, he told Czech newspaper Hospodarske Noviny in an interview conducted in Prague last week. Still, it may also be possible for Britain to both maintain free trade with the EU and keep control over its borders, he said.

"It's bollocks to say that the free movement of people is a fundamental right," Mr Johnson said in the interview, according to a transcript translated into Czech in the newspaper. The movement of people "across Europe isn't something that was in the founding Rome treaties from 1957, it wasn't in the Nice treaty, and it wasn't in the Maastricht treaty either," he said, according to the newspaper.

The question of remaining in the 28-member bloc's customs union has divided British Prime Minister Theresa May's government, with Mr Johnson, Brexit Secretary David Davis and Trade Secretary Liam Fox agitating to leave and Chancellor of the Exchequer Philip Hammond counselling caution.

Leaving the customs union would allow Mr Fox to try for trade deals with countries such as China, which he currently can't. Still, that would mean Britain's exporters would likely face costly delays and bureaucracy at customs.

Leaving the customs union is "an issue that will be discussed", Mr Johnson told the paper. "I believe it can be done, and at the same time maintain free trade."

The customs union allows EU members to impose no tariffs on goods traded among each other and sets a common duty on goods of non-EU members. The EU gains leverage in trade negotiations, since it represents a bloc of 500 million people.

Mr Chuka Umunna, a Member of Parliament and supporter of Open Britain, a group that supports unrestricted trade and investment with Europe, said leaving the customs union could hurt UK businesses.

"A decision on whether to leave the customs union is a huge choice that should be debated in Parliament, not decided off the cuff on a visit to Prague," Mr Umunna said in a statement. "Businesses will be deeply concerned. The customs union minimises bureaucracy at borders, which facilitates trade and business expansion."

Mr Johnson also said there were reasons to be optimistic following Mr Donald Trump's US election victory, as the real-estate magnate knows how to make deals and "strongly believes in values" including freedom and democracy.

"If I understand his opinions, then in many aspects he's a liberal guy from New York," Mr Johnson said. "Let's wait and see what his policies are."