Cameron warns Johnson breaking the law is 'not a good idea' ahead of crucial Supreme Court ruling

David Cameron has warned Boris Johnson that breaking the law is "not a good idea" ahead of a critical ruling from the Supreme Court on the suspension of parliament.

In just days, the UK's highest court will determine whether the prime minister's decision to prorogue parliament until 14 October was unlawful.

The former Tory prime minister told Sky News' Sophy Ridge he had been in contact with Mr Johnson, and told him: “No deal is not a good idea. Breaking the law is not a good idea. Focus everything you’ve got on getting that deal, and that’s what he’s doing, to be fair to him.”

Mr Cameron added he not yet had a one-to-one meeting with Mr Johnson, but added: "He's very busy. He knows my views on most things.

"The most important thing he is trying to do, he has my support for, which is going to Brussels, getting a deal, bringing that deal and trying to end this period of uncertainty and I wish him well as he does that."

On the case, Labour's shadow Brexit secretary and former director of public prosecutions Sir Keir Starmer, said: "I'm not sure why the judgement needs as much time as it's being given – it's fairly short, easy judgement, isn't it?

"He's lied to every other woman he's ever met – why would he make an exception for the Queen? Proroguing overturned."

A panel of 11 justices heard appeals over three days arising out of separate legal challenges in England and Scotland, in which leading judges reached different conclusions.

At the close of the unprecedented hearing on Thursday, the court's president Lady Hale said the judges hope to give their decision early next week.

She said: "I must repeat that this case is not about when and on what terms the United Kingdom leaves the European Union.

"The result of this case will not determine that. We are solely concerned with the lawfulness of the Prime Minister's decision to advise Her Majesty to prorogue Parliament on the dates in question.

"As we have heard, it is not a simple question and we will now carefully consider all the arguments that have been presented to us."