U.K.’s Brexit strategy called ‘impossible, politically unavailable’ by EU officials

LONDON—Foreign Secretary Boris Johnson, a leader of the Brexit movement, is Britain’s top diplomat and tasked with winning international friends as the country prepares its exit from the European Union.

So far, that’s turning into mission impossible, as EU leaders accuse him of offering insubstantial and unrealistic visions of the U.K.’s future outside the 28-nation bloc.

The latest critic is Dutch Finance Minister Jeroen Dijsselbloem, who told the BBC on Tuesday that Johnson “is offering to the British people options that are really not available.”

“There is no win-win situation” with Brexit, Dijsselbloem said. “It is going to be a lose-lose situation.”

Johnson is one of Britain’s best-known politicians, famous at home and abroad for his tousled hair, rumpled appearance and florid speeches studded with Latin phrases. A leader of the victorious “leave” campaign in Britain’s EU membership referendum, he was named foreign secretary when Prime Minister Theresa May took office in July.

For the last few months he has been touring EU capitals ahead of formal exit talks, expected to start next year.

British officials have been reluctant to provide details of what deal they hope to strike with the bloc. But Johnson was quoted this week by the Czech newspaper Hospodarske Noviny as saying the U.K. would likely have to leave the EU customs union, while retaining access to the bloc’s single market in goods and services.

The customs union and the single market are both pillars of the EU’s model of tariff-free trade within its bloc of 500 million people. Members of the customs union trade tariff-free, but impose common levies on imports from outside the union.

Dijsselbloem—who also heads the group of 19 countries who use the common euro currency—said Johnson “is saying things that are intellectually impossible, politically unavailable.”

“To say, ‘We could be inside the internal market, keep full access to the internal market, but be outside the customs union’—this is just impossible, it doesn’t exist,” Dijsselbloem told the BBC’s “Newsnight” program.

“The U.K. will be outside the internal market and there will be some hindrances,” he said. “The full free movement within the internal market can only be available if the U.K. also accepts the other freedoms of Europe, including migration within Europe.”

Immigration was a major issue for many Britons who voted to leave the EU, and British officials insist they will end the free movement of people from the bloc into Britain—although few details of the plan have yet been provided.

Johnson is widely mistrusted in Brussels from his time as a journalist there, when he helped cement the EU’s image in Britain as a bureaucratic behemoth obsessed with cumbersome regulation.

That friction has not abated.

Johnson declined to attend a special meeting Sunday of EU foreign ministers to discuss the win of U.S. President-elect Donald Trump, and told his EU counterparts to stop the “collective whinge-o-rama” over the U.S. election result.

He recently drew skepticism in Italy when he said the country should continue free trade with the U.K. because Britons consume a lot of prosecco. Similarly, in Germany, he stressed the large number of German cars bought in the U.K.—fostering a sense that Britain takes other EU countries for granted.

After Johnson said in September that it was “complete baloney” to suggest an automatic link between free movement and single-market membership, Germany Finance Minister Wolfgang Schaeuble said he’d be happy to send him a copy of the EU’s central Lisbon Treaty and explain it “in good English.”

Charlotte Galpin, a postdoctoral researcher at the University of Copenhagen who studies Euroskepticism, said Johnson’s diplomatic efforts are appearing counterproductive.

“My sense … is that they listen to him saying these things and think ”What is he talking about? This is not how the EU works,’“ she said.