Labour would take Britain out of the European single market were it in charge of negotiating Brexit, leader Jeremy Corbyn has said, creating more divisions with his pro-EU MPs.

Corbyn said the UK must quit the common market because it is “inextricably linked” to the EU. He said, however, his party had not decided its position on membership of the Customs Union, which places tariffs on imports from around the world and stops Britain negotiating trade deals.

Labour’s 2017 election manifesto pledged to focus on “retaining the benefits of the single market and customs union” but was not explicit on whether Britain would actually remain inside the institutions.

“The single market is dependent on membership of the EU. What we have said all along is that we want a tariff free trade access to the European market and a partnership with Europe in the future,” Corbyn told the BBC.

“The two things are inextricably linked so the question then is the kind of trade relationship of the future and we have made it very clear we want a tariff free trade access with the European market.”

Corbyn added that his party had not decided whether it would keep Britain inside the customs union, having not “jumped on either side of that fence.”

Corbyn’s remarks are the strongest sign yet that the party rejects the “Norway option,” under which Britain would remain part of the single market by staying in the European Economic Area (EEA).

His comments have sparked opposition from Remain-supporting Labour MPs, who cited Norway, Iceland, and Liechtenstein as examples of non-EU nations that are part of the single market via the EEA.

Frontbencher Chuka Umunna, the pro-EU Labour MP for Streatham, said: “The overwhelming majority of Labour members think we should be fighting to stay in the single market. Let’s do it.”

Last month, Umunna tabled an amendment to the Queen’s Speech calling for Britain to remain in the single market. It was backed by 48 Labour rebels who defied the party whip, which had ordered them to abstain.

UK Prime Minister Theresa May has said the Tories want to leave both the single market and the customs union.

The single market is the guarantee between members that they will scrap tariffs and quotas and harmonize regulations with one another to help the flow of trade in goods, services, and people.

The customs union, which is separate, is an agreement between its members that they will charge the same external tariffs to countries outside it.

Corbyn’s announcement comes as a new poll shows public opinion has shifted in favor of securing access to the European single market after Brexit rather than full control over immigration.

Asked by Ipsos Mori researchers what should be the priority in negotiations, 49 percent preferred keeping access to the single market of 500 million European consumers.

Only 41 percent said they would put control over immigration first, according to the Evening Standard.

The lead suggests there would be support for Brexit Secretary David Davis if he can secure a trade deal that avoids a hard Brexit, despite evidence that the public wants to see a drop in immigration levels.

The two goals are seen as incompatible because membership of the single market would require the free movement of workers between the EU and the UK.