LONDON (AP) — A pro-Europe think tank says it is willing to take the British government to court to try and keep the U.K. in the European Union single market once it leaves the bloc.

The group British Influence argues that leaving the EU does not automatically mean leaving the larger European Economic Area, whose members belong to the EU's tariff-free single market in goods and services.

In return, EEA members, including Norway and Iceland, pay into EU coffers and accept free movement from member states.

The British government says the U.K. will leave the EEA once it quits the EU.

British Influence said Monday it has asked Brexit Secretary David Davis to clarify the government's position, and will go to court if ministers insist leaving the EU means leaving the single market.