Theresa May is expected to announce plans to abandon the single market in a bid for hard Brexit – but this may be made more difficult by a legal challenge relating to a clause known as Article 127.

Unlike Article 50, which is the subject of its own Supreme Court battle to be resolved this week, Article 127 of the European Economic Area agreement sets out the mechanism for leaving the single market.

Pro-EU campaigners say Britain will have to organise its extraction from the European Economic Area (EEA) – and therefore the single market – separately to its departure from the EU itself.

The case, which was initially proposed last year by pressure group British Influence, has been postponed and will now be heard in early February, reported City AM.

It argues that Parliament should be able to vote on triggering Article 127, despite the government’s wish for single market membership to end when Britain leaves the EU.

Whether or not the case proceeds to a full trial, as the Article 50 challenge has done, depends on the outcome of the hearing, which was due to take place this week.

The EEA agreement was first drawn up in 1994 between the EU member states and three countries not in the EU: Iceland, Liechtenstein and Norway.

Supreme Court Brexit Challenge Show all 13 1 /13 Supreme Court Brexit Challenge Supreme Court Brexit Challenge People wait to enter the public gallery outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Gina Miller, co-founder of investment fund SCM Private arrives at the Supreme court in London on the first day of a four-day hearing Getty Supreme Court Brexit Challenge A man waves the EU flag in front of the Supreme Court Getty Supreme Court Brexit Challenge Satirical artist Kaya Mar poses with two of his paintings in front of the Supreme Court Getty Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin. The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge The eleven Supreme Court Justices will hear the government's appeal, following the High Court's recent decision that only Parliament can trigger Article 50 Getty Supreme Court Brexit Challenge Businesswoman Gina Miller arrives at the Supreme Court ahead of the first day of a hearing into whether Parliament's consent is required before the Brexit process can begin Getty Supreme Court Brexit Challenge Attorney General Jeremy Wright arrives at the Supreme Court in London EPA Supreme Court Brexit Challenge Protesters outside the Supreme Court in London, where the Government is appealing against a ruling that the Prime Minister must seek MPs' approval to trigger the process of taking Britain out of the European Union PA wire Supreme Court Brexit Challenge A protesters wearing a judge's wigs and robes stands outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge A protester holds up a placard outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters Supreme Court Brexit Challenge Pro-Europe protestors dressed as Supreme Court Justices stand outside the Supreme Court Getty Supreme Court Brexit Challenge A man waiting to enter the public gallery waves a European Union flag outside the Supreme Court ahead of the challenge against a court ruling that Theresa May's government requires parliamentary approval to start the process of leaving the European Union, in Parliament Square, central London Reuters

Article 127 of the agreement states that “Each Contracting Party may withdraw from this Agreement provided it gives at least twelve months' notice in writing to the other Contracting Parties”.

Ms May is expected to reveal more details on the Government’s strategy to leave the EU potentially just days before the crucial Supreme Court ruling on whether Parliament must give its consent to leaving the EU.