At the High Court in London, the Lord Chief Justice Lord Burnett and two other judges rejected businesswoman Gina Miller's challenge, finding that the prorogation was "purely political" and not a matter for the courts.
The two European leaders back the shorter proposal so as to prepare the bloc for the UK's exit on October 31st, with the Finnish prime minister adding in comments reported by The Sun: "We need to know what the United Kingdom is proposing".
Mr Johnson, who has said he wants to leave the European Union - preferably with a deal - on 31 October, has urged the European Union to scrap the backstop. "We know that this case must be resolved as quickly as possible, and we hope to be able to publish our decision early next week", judge Brenda Hale said as the third and final day of hearings wrapped up.
Finnish Prime Minister Antti Rinne said Mr. Johnson had less than two weeks to come forward with concrete proposals to break the logjam over Brexit. They also accuse the prime minister of misleading Queen Elizabeth II, whose formal approval was needed to suspend the legislature.
In a dramatic attack by one former Conservative leader on another, Major alleged "the reasons set out in the documents put before the court by the prime minister can not be true", his lawyer Edward Garnier said.
During the hearing, the court was shown a handwritten note in which Johnson had described the parliamentary session as "a rigmarole.to show the public that MPs were earning their crust".
The Brexit agreement made with the European Union by Johnson's predecessor, Theresa May, was rejected three times by Britain's Parliament, prompting May to resign and the fiercely pro-Brexit Johnson to come to power in July. David Cameron, who resigned after the Brexit referendum in 2016, has also been scathing.
Lord Keen, representing the British government, said that prorogation, or suspension of parliament, could be done for political purposes. She resigned earlier this year. Rival pro-EU and pro-Brexit demonstrators gathered daily outside the courthouse on London's Parliament Square.
"The result of this case will not determine that".
"We are exclusively concerned with the lawfulness of the prime minister's decision to advise Her Majesty to prorogue parliament on the dates in question", she said.
Lawyers representing the prime minister told the court during the two previous days of hearings that the dispute over the suspension was a political issue, not a matter for judges, and that Johnson's objective was not improper.
It's not clear what they would do there, since there is no business scheduled.
But the European Commission, which leads Brexit talks for the remaining 27 member states, gave a more sober assessment, stressing that the British papers amounted to no more than "a first set of concepts, principles and ideas".
Mr. Major joined the attack on his successor, arguing in a written filing that Mr. Johnson had not been truthful and that the court must intervene.
The government could also start the new session of Parliament - now scheduled to begin October 14 - earlier than planned.
"You ask me if I am optimistic or pessimistic. the famous grandfather of the EU, Jean Monnet, said "I am not optimistic, I am not pessimistic, I am still determined", he said.
"I will wait to see what transpires", he said.
Finland now holds the rotating presidency of the Council of the European Union, and the EU's other 25 Member States will have to agree to this new deadline, the original agreed as the 17th of October, the date of the European Summit.
Finland now holds the rotating presidency of the 28-nation bloc.