The Prime Minister is facing another legal challenge today over his plan to suspend Parliament for five weeks this month.
The hearing at the High Court in London comes the day after he fought off a similar action in Scotland.
An urgent application for a judicial review into Johnsons decision was launched by pro-remain campaigner Gina Miller.
The businesswoman successfully challenged the Government at the High Court in 2016 over the triggering of the Article 50 process to start the Brexit countdown.
Former Tory Prime Minister Sir John Major has thrown his weight behind Ms Millers action, demonstrating how much Brexit is tearing his party apart.
The application will be supported by statements from Sir John, Shadow Attorney General Baroness Shami Chakrabarti and lawyers from the Scottish and Welsh governments.
Other politicians including Labour Party deputy leader Tom Watson, Liberal Democrat leader Jo Swinson and Labour MPs Jess Philips and Alex Sobel are understood to have had their applications to join the case rejected.
Advertisement
Advertisement
Johnson has insisted it is completely untrue that his plan to suspend Parliament from the second week of September has anything to do with Brexit.
He said a new Queens Speech on October 14 to re-open the Commons is needed so his new government can introduce an exciting agenda of legislation.
But many people are not buying it, accusing him of trying to prevent MPs from being able to block a no-deal Brexit before October 31, sparking mass protests across the country.
Todays bid to challenge the legality of the prorogation of Parliament will be heard by the Lord Chief Justice Lord Burnett and two other leading judges.
The decision made in Scotland being challenged with an appeal due to be heard today (Picture: PA)
It is expected to last all day and will be heard by Lord Chief Justice Lord Burnett of Maldon, Master of the Rolls Sir Terence Etherton and President of the Queens Bench Division Dame Victoria Sharp.
If they decide the case can proceed before arguments surrounding the case are heard immediately afterwards.
Ms Millers challenge is based on the legitimacy of Johnsons advice to the Queen before she accepted his request to suspend Parliament.
