The European Union has told British firms they will lose some access to European markets if the country insists on restricting migration from the EU.
Wednesday, European Commission President Jean-Claude Juncker said the U.K. couldn't pick and choose what it liked about the EU once it has left.
Brits voted to leave the European Union in a referendum in June, but the government has since failed to reveal any details about how it plans to reshape relations with its most important trading partner.
British Prime Minister Theresa May has said she will aim for "the best possible deal" for her country in Brexit talks with the EU, without saying what that means. Former PM David Cameron, who pushed for a referendum on a possible exit from the EU, has since resigned as both prime minister and member of parliament.
The all-important U.K. financial services sector is pushing for full access to Europe's free trade area, the world's largest. And many foreign companies operating in Britain have said losing access could force them to move people and operations out of the country.
But many pro-Brexit politicians in the U.K. have insisted that migration from the EU must be more tightly controlled once the country has left the group. No other country has full access to EU markets without accepting free movement of EU citizens across its borders.