Parliament should vote on the UK leaving the European Economic Area, says a think tank
London (AFP) - The British government on Monday faced the prospect of a fresh Brexit legal challenge over whether it will automatically leave the tariff-free European Economic Area when it quits the EU.
Pro-EU think-tank British Influence said there was a "strong chance" the government would be acting unlawfully if it took Britain out of the EEA as well as the European Union.
"We need judicial clarification," it said.
But British Prime Minister Theresa May's spokeswoman told reporters: "Once we leave the EU, we will automatically cease to be a member of the EEA."
The EEA, which allows for tariff-free trade and free movement of people, includes all 28 EU member states as well as Norway, Iceland and Liechtenstein.
While the EEA does not overlap exactly with the single market, the debate will play into a fierce row in Britain about what access British companies will have to European markets following Brexit.
British Influence's announcement immediately came under fire from pro-Brexit lawmakers, who said it was another attempt to undermine the result of the June referendum in which Britain voted to leave the EU.
Conservative MP and Brexit supporter Dominic Raab accused the lawyers of "coming up with new legal wheezes to try and frustrate the will of the people".
"The public have spoken. We should respect the result and get on with it, not try to find new hurdles that undermine the democratic process."
But George Yarrow, an Oxford University professor, told the BBC: "There is no provision in the EEA Agreement for UK membership to lapse if the UK withdraws from the EU".
- Brexit 'can be stopped' -
Supreme Court judges are due to hear a separate case next month on whether or not the government needs the formal consent of parliament to trigger Article 50 of the Lisbon Treaty, the procedure for leaving the EU.
A ruling on that case is expected in January and, if the government loses, it could delay May's plan for invoking Article 50 by the end of March at the latest.
Several senior figures including former British prime ministers Tony Blair and John Major have also said a second referendum on a Brexit deal is possible.
Blair has gone further, suggesting that Brexit could be cancelled entirely even after Article 50 is invoked if the government changes its mind before Britain officially leaves the 28-nation bloc.
Brexit "can be stopped if the British people decided, having seen what it means, the pain-gain cost-benefit analysis doesn't stack up," Blair told the New Statesman magazine.
May has promised to cut immigration from the European Union -- a central theme during the EU referendum campaign -- while also retaining as much access as possible to the EU's single market for businesses.
EU leaders have ruled out these aims as incompatible.