Boris Johnson was considering the suspension of Parliament two weeks before it was made public, court documents suggest.
In a note dated August 15, Number 10's former legislative affairs director Nikki da Costa asked whether an approach to prorogue Parliament should be made.
A note of "yes" was written on the document, with a handwritten note by the Prime Minister the next day calling the September session of Parliament a "rigmarole".
The details emerged at a hearing in the Court of Session to consider whether a judge should halt Johnson's move to shut down Parliament.
Lord Doherty last week refused a request to grant an interim ruling on the case, but moved the full hearing on it forward to Tuesday from Friday.
The action has been backed by around 75 cross-party MPs and peers, including SNP MP Joanna Cherry and Lib Dem leader Jo Swinson.
The notes presented to court also revealed Johnson believed it should not be "shocking" to suspend Parliament, as he suggested MPs only wanted to come back in September to show they were "earning their crust".
Aidan O'Neill QC, representing the parliamentarians, described the Prime Minister as having a record that was "characterised by incontinent mendacity, an unwillingness or inability to speak the truth".
He pointed to the documents as showing the suspension of Parliament policy was being considered much earlier than announced and argued the court had been misled.
Mr O'Neill said: "This court was told nothing of that and was told in fact that this judicial review is academic, hypothetical and premature.
"That is not true. This court and these petitioners were being actively misled."
He argued the real reason to suspend Parliament was to allow a no-deal Brexit to take place by removing proper scrutiny.
Mr O'Neill said decisions in two separate Brexit-related court cases, brought by activist Gina Miller and Andy Wightman MSP, show Parliament should decide whether or not the UK leaves without a deal.
He claimed it was not lawful to create circumstances where that happens without such approval.
David Johnston QC, representing the Government, said the arguments were "academic" as it was for the Queen, not for the courts, to decide if Parliament can be prorogued
The Queen met the Privy Council on August 28 to approve prorogation, which First Minister Nicola Sturgeon branded "a dark day for democracy".
A full interdict by the Scots judge would immediately lift the royal order to suspend Parliament, although the UK Government has said it would be certain to appeal it.
The ruling is expected on Wednesday.
By special correspondent Bernard Ponsonby
Submissions to courts are normally the stuff of ponderous and formal language delivered with a politeness which can leave the observer wondering why on earth the parties are at war in the first place?
Step forward Aiden O'Neill QC. His characterisation of the Prime Minister would invite a writ for defamation if uttered elsewhere. Boris Johnson has a record characterised by "incontinent mendacity" and he was unwilling or unable to "speak the truth".
Just in case Lord Doherty missed the point, the government was characterised as "autocratic" using "one-man rule".
Why so personal? Why so political when this case will ultimately turn on law, albeit greatly influenced by politics?
Put simply what Mr O'Neill is trying to do is to torpedo the government's assertion that they are not dodging parliamentary scrutiny of a no deal Brexit and that the Queen assenting to the suspension of parliament was just the use of a well established protocol of behaviour.
The charge is that prorogation and prerogative powers were being abused because the government's motives were to avoid parliamentary scrutiny.
Lord Doherty has an unenviable question to answer. Even if a government's motives are not as they state in seeking to suspend parliament, does that give the court the authority to determine that the suspension should be set aside?
And a further point. How is it possible to determine that the government's motives are not as they state without hearing from those who sought the suspension?
Perhaps some clarity when the UK Government's position is put to the court. Then again, this is Brexit related, perhaps not.