The European Union is giving the U.K. a take-it-or-leave-it offer over customs union membership.

Remaining in the regime must be on the EU’s terms, the conditions won’t change, and it would mean Britain having no independent trade policy, Brexit negotiator Michel Barnier warned.

“We can’t change our rules; our rules will remain the same,” Barnier told a business conference in Sofia on Thursday. “When you’re in a customs union for goods, like Turkey for example, you become part of a common trade policy—you don’t have autonomy anymore.”

Bloomberg reported on Wednesday that the EU would be prepared to offer Britain a better deal than the one it gave Turkey, which participates in the regime but which doesn’t have any influence over global trade deals. Barnier’s remarks on Thursday indicate that while the U.K. may be consulted over trade policy if it opted to stay in the customs union, Britain’s position would still be less favorable than those of EU members, and it would come with conditions attached.

Focal Point

Barnier’s comments add further fuel to the customs union question that has become the focal point for debate over the type of relationship the U.K. wants with the EU after Brexit. While some reports indicate U.K. Prime Minister Theresa May might be getting ready to keep Britain in the arrangement despite public statements to the contrary, she appears again to have ruled it out.

“This is a decision the U.K. government has to take,” Barnier said.

At a meeting on Tuesday, the prime minister reassured Brexit-backing members of her party that she will deliver the kind of Brexit they want and will take Britain out of the customs union., according to two people familiar with the conversation.

When the EU published its vision for the two sides’ future relationship at a summit in March the bloc said it would revise them when leaders reconvene in June to take account of any changes in U.K. policy. Some EU officials in Brussels say they believe the government may be willing to take a softer line after local elections in the U.K. on May 3.

Barnier, who is scheduled to give a second speech later on Thursday on financial services, reiterated that, with the red lines as they are, the U.K. can’t expect more than a free-trade deal of the sort the EU has given to Canada or Japan.