Ministers are considering 16 key words to formally begin Britain’s journey to leaving the European Union as they prepare for defeat in the Supreme Court.

They are so determined to start Brexit talks by the end of March, even if judges demand they get parliamentary approval, that a Bill just a few sentences long is being drafted.

A Whitehall source said the key clause will demand MPs “give permission to the British Government to trigger Article 50 of the Treaty on European Union”.

The draft legislation is being kept as short as possible to stop pro-EU politicians amending it with demands for Theresa May to reveal her Brexit negotiation stance.