'This is a huge thing': Labour Brexit chief Keir Starmer reacts to parliament suspension being ruled unlawful after being told of news while live on stage

Labour's Sir Keir Starmer has hailed a court ruling against Boris Johnson's suspension of parliament as "huge" after being told of the decision live on stage.

The shadow Brexit secretary declared, "I'd better get back to London", when he was informed after a speech to the TUC in Brighton that Scotland's highest court had ruled the prorogation to be unlawful.

In a unanimous decision in Edinburgh’s Court of Session, three judges ruled that the prorogation was unconstitutional, but no order was given to reverse it ahead of a full hearing at the Supreme Court on Tuesday.

Sir Keir vowed to "get Boris Johnson back in parliament" to hold him to account over Brexit.

He told delegates: "It was obvious to everybody that not only was shutting down parliament at this crucial time obviously, the wrong thing to do, we should be sitting each and every day to resolve this crisis.

"But that the prime minister was not telling the truth about why he was doing it."

Sir Keir added: "This is really important. The idea of shutting down parliament offended people across the country and then they felt they weren’t being told the truth - and that sums up the man.

"I’m really pleased with this result. I’m surprised because for a court to make a declaration like that on an issue like this is a huge thing for us.

"It vindicates everything we’ve done last week and I think what I can do and what others need to do is get back to parliament, see if we can’t open those doors and get back in and get Boris Johnson back in parliament so we can hold him properly to account."

A government spokesman said it was planning to appeal the decision in the Supreme Court.

The news broke as Sir Keir was delivering a keynote address to hundreds of trade unionists in Brighton, where he said a referendum was the only was to break the Brexit deadlock.

"We have to draw a line under the wasted years of Tory rule and failed negotiations, we will have to break the deadlock and clean up the mess left by the Tories," he said.

"A referendum is the only way to do so. And that is why Jeremy was right to say at Congress yesterday that an incoming Labour government will commit to a referendum.

"And – of course – ‘remain’ should – and it will – be on the ballot paper, along with a credible option to leave. We need to ask the public whether they are prepared to leave on the terms on offer or whether they would prefer to remain."

It comes as the Labour leader ramped up planning for an autumn election, meeting union leaders to set out a manifesto policy which would see the party offer a referendum choice between “credible” Remain and Leave options without committing itself to backing either side.

But Labour divisions were laid bare when Tom Watson, the deputy leader, insisted that a referendum should come before an election.

In a separate speech in London, Mr Watson also argued that if an election comes first, Labour should fight it “unambiguously and unequivocally” backing Remain.