Political parties across Britain and Ireland have urged British Prime Minister Boris Johnson to resign following an unprecedented ruling on Tuesday by the Supreme Court in London that his suspension of the Westminster parliament was unlawful.

The decision of the eleven judges on the panel was announced by the court’s president Lady Hale. She said this was not a normal prorogation of parliament, and it took place in “quite exceptional circumstances”.

“The decision to advise her majesty to prorogue parliament was unlawful because it had the effect of frustrating or preventing the ability of parliament to carry out its constitutional functions without reasonable justification,” she said.

The speaker of the British House of Commons has said that Westminster will resume its business this morning.

Despite a unanimous decision, there were lingering doubts over whether Johnson’s extreme-right administration would even recognise the parliament’s return. He has previously declared his willingness to ignore the rule of law in pursuit of a Brexit deadline of October 31.

Johnson said he “strongly disagrees” with the court ruling but that he accepted that Westminster “will come back”.

Speaking from New York he said: “As the law currently stands, the UK leaves the EU on October 31st come what may. But the exciting thing for us now is to get a good deal, and that is what we are working on. And to be honest it is not made much easier by this kind of stuff in parliament or in the courts.”

Sinn Fein vice-president Michelle O’Neill said: “This is another one of those meltdown moments” for the current Tory regime and that “Boris Johnson should go”.

“What is demonstrates for me is more of the chaos, the dysfunction, the mess that is happening and unfolding day on day in Westminster.”

Opposition Labour leader Jeremy Corbyn said Johnson’s contempt for democracy and his abuse of power had been exposed.

“A Labour government would want to be held to account. I invite Boris Johnson in the historic words to consider his position.”