The government is facing another legal battle over Brexit, according to reports - and more specifically, over whether the UK will stay inside the Single Market once its leaves the EU.
Lawyers are preparing to challenge the government's stance that Britain's European Economic Area membership ends when it exits the EU, the BBC has reported.
Instead, they say uncertainty over EEA membership means that ministers could be stopped from taking the UK out of the Single Market - and that it is a matter for parliament to decide.
The pro-Single Market think tank British Influence has informed Brexit secretary David Davis that it will seek a formal judicial review of the government's position.
The move follows reports that MPs are prepared to fight their corner in a battle with Theresa May over access to the Single Market. In October, a number of MPs stated publicly that the Prime Minister has no mandate to take the UK out of the Single Market.
Former Labour leader Ed Miliband, former Conservative ministers Nicky Morgan and Anna Soubry, and former deputy prime minister Nick Clegg, among others, want to force May to appear before parliament to explain the role of MPs in future Brexit decisions.
Meanwhile, the government is already embroiled in a legal row over Brexit, as it prepares for the next stage of its court battle on triggering Article 50.