BORIS Johnson has been branded a “spoilt brat” by Labour and of being “in contempt of Parliament” by the SNP after he got a senior diplomat to send an unsigned photocopy of the letter, required by law, asking the EU for a Brexit extension.

The Prime Minister sent a second note, signed by himself, to Donald Tusk, the European Council President, underlining his personal view that any further extension would be "deeply corrosive".

John McDonnell, the Shadow Chancellor, told Sky News's Sophy Ridge on Sunday: "He may well be in contempt of Parliament or the courts themselves because he's clearly trying to undermine the first letter by not signing the letter.

"He's behaving a bit like a spoilt brat. Parliament made a decision, he should abide by it and this idea that you send another letter contradicting the first letter flies in the face of what both Parliament and the courts have decided."

The SNP also suggested Mr Johnson could be in contempt of Parliament by not adhering to the spirit of the undertaken given to the Scottish courts, raising the prospect of possible court action against the PM this week.

SNP MP Joanna Cherry, who brought the case which led to Mr Johnson's suspension of Parliament being ruled unlawful, branded his approach to the legally required letter "pathetic" as she vowed to put the decision before the courts.

She tweeted: "Boris Johnson promised Scottish court he would comply with Benn Act & not seek to frustrate it. Looks like he's breaking both promises. Fortunately, no need to raise new proceedings, our existing case is back in court on Monday."

But Dominic Raab, the Foreign Secretary, insisted the PM had “complied with the law”.

He told BBC TV’s Andrew Marr Show: “He has made clear his view hasn’t changed; Parliament can’t muzzle the PM. He doesn’t want an extension.”

Following the Commons defeat on Saturday when MPs voted that Brexit legislation had to be passed before the UK-EU deal was formally ratified, Mr Johnson rang European leaders as well as Donald Tusk, the European Council President, declaring that the formal letter he had sent was “Parliament's letter, not my letter".

It was accompanied by a note from Sir Tim Barrow, the UK ambassador to the EU, making clear the letter was only being sent to comply with the law.

The PM then sent another letter, carefully checked by Whitehall lawyers, making clear the Government would continue to seek to ratify the deal and that Brussels should do the same, adding how more delay would “damage the interests of the UK and our EU partners”.

The notes were made as the PM also wrote to all Tory MPs and peers insisting that he would tell Brussels a further Brexit delay was "not a solution" to the situation.

In a letter, he told them: "I will tell the European Union what I have told the British public for my 88 days as Prime Minister: further delay is not a solution."

He added: "It is quite possible that our friends in the European Union will reject Parliament's request for a further delay [or not take a decision quickly]."

The PM also on Saturday discussed the situation with Emmanuel Macron, the French President, who has made clear his opposition to the EU27 granting a further extension to Brexit.

Meanwhile, Ian Blackford, the SNP leader at Westminster, raised the prospect of Mr Johnson finding himself in court over the issue of whether he had abided by the law to not frustrate the process of requesting an extension as set out in the Benn Act.

The Highland MP also questioned how many unsigned letters the PM had sent since taking over in Downing St.

Speaking on the BBC's Sunday Politics Scotland programme, Mr Blackford was critical of Mr Johnson's move to express a personal opinion in a second letter to the EU, noting: “There is a clear case that he is in contempt of Parliament."

He explained: "The key letter, the one seeking the extension, seems to be a photocopy of the instruction that he has been given by Parliament and the courts and he's unsigned. It really does beg the question how many other unsigned letters has Boris Johnson sent as Prime Minister?”

The party leader went on: "He's not treating the office of Prime Minister with any respect or any dignity, it will be a matter for the courts.

"There is an issue as to whether or not he's in breach of the court given what happened a couple of weeks ago given what happened when Joanna brought her action but certainly there's an issue about being in contempt of Parliament.

“The court also made clear that if the Prime Minister didn't follow the letter of the law, then the court would expect to make a judgement on that so I would strongly suspect you may see action taking place in the court over the course of the coming days.”

Mr Blackford added: "We'll take our responsibilities in Parliament and we have got an extraordinary week in front of us. There is a clear case that he is in contempt of Parliament in the way he's acting. Others will take their responsibilities through the legal process."

Luke Graham, the Scottish Tory backbencher, also insisted Mr Johnson had written the letters “in accordance with the law” and now the Government was focused on getting the deal through Parliament.

Stressing how avoiding a no-deal outcome was what his party had been trying to do all along, the Ochil and South Perthshire MP said: "What we saw in the last week is the Prime Minister actually deliver a deal that delivers on a lot of the objectives that we were trying to achieve as a country.

"There's less discussion about no-deal, it's a discussion about we've got a deal, the EU have agreed it, it's now for us to agree it as well.”

Mr Graham added: "We've got one on the table and it's time for MPs right across the House of Commons to come together and actually vote for that deal so we can move forward."