The Supreme Court will rule early next week on whether it was legal for Boris Johnson to shut Parliament down.
And Government lawyers warned the Prime Minister could prorogue Parliament for a second time even if the court rules against them.
The government's lawyers Sir James Eadie and Lord Keen have set out how they will respond to a range of possible rulings by the court.
One possible scenario is that the 11 judges find this suspension was unlawful, but their reasoning leaves open the possibility of proroguing Parliament for the same period in a lawful way.
The document says: "In that scenario, the court would and could not make any order purporting to require Parliament to be reconvened... Parliament would remain prorogued."
It came after John Major today sensationally attacked his Downing Street successor in the Supreme Court in an unprecedented PM-on-PM row.
Lawyers for the former Tory Prime Minister hit out at Boris Johnson as he joined a three-day legal fight against the decision to shut down Parliament. Representing Sir John, a top QC said the reasons Boris Johnson gave for suspending parliament for five weeks from September 9 were not "true and complete".
He warned the UK's highest court must not be “naive” to take the PM's position - that he simply prorogued Parliament to hold a Queen's Speech - at face value.
And in separate legal papers, Sir John even compared Mr Johnson to a dishonest estate agent and claimed he had 'ulterior motives' for suspending Parliament.
It echoes criticisms from campaigner Gina Miller and MPs and peers who brought an original case in Scotland, who all say Mr Johnson's real intention was to shut down debate on Brexit .
