Kemi Badenoch just showed why Andy Burnham is about to make a fatal mistake. It’s believed that Mr Burnham’s first choice for the key role of Chancellor is Ed Miliband. But the Conservative leader demonstrated why Mr Miliband is unfit for the job.

It’s not too late for Andy Burnham, the former Greater Manchester Mayor, to change his mind. Once he walks into No 10 as Prime Minister, he could name someone else to take over at the Treasury. And on the basis of today’s session of Prime Minister’s Questions in Parliament, he must be seriously considering doing just that.

Mr Miliband wasn’t even in the room to hear Mrs Badenoch demolish his record. She started by turning her guns on the current Chancellor, Rachel Reeves, saying: “She’s the one who snatched the winter fuel payment, she’s the one who announced a disastrous budget that killed economic growth, and because of her, once again a Labour Prime Minister is leaving office with unemployment higher than when he came in.”

But the Tory leader knows that Ms Reeves will leave her job at the same time as Prime Minister Sir Keir Starmer. There’s no point criticising her – so instead Mrs Badenoch turned her attention to Mr Miliband, the current Energy Secretary, who was Labour leader himself from 2010 to 2015.

Mrs Badenoch said: “But the Chancellor isn’t the only person who let him down, the Energy Secretary is putting up bills and killing jobs. He was a failed Labour leader, rejected by the electorate, brought back from the wilderness by this man, and when the going got tough, he jumped into bed with the mayor of Manchester.”

And she reminded MPs that Mr Miliband has form – telling them: “It’s not the first time he’s betrayed someone close to him, is it?”

This is a reference to the idea that Mr Miliband betrayed his own brother, David, back when they were both ambitious young Labour MPs.

David Miliband, by all accounts, was considering standing for the Labour leadership and challenging the sitting Prime Minister, who at that point was Gordon Brown.

Ed supposedly talked him out of it and urged him to wait.

When Mr Brown eventually lost the 2010 General Election and resigned, there was a vacancy for Labour leader – and David Miliband declared himself a candidate.

But guess what? Ed Miliband also took the opportunity to stand for the leadership. And he won.

Opinions differ over whether Ed really did anything wrong. Some people would argue he had every right to stand as a leadership candidate.

But others see him as a slippery character who stabbed his brother in the back.

And it does look a lot like he has now stabbed Sir Keir in the back too, calling on him to quit (in a private conversation that somehow became public) and joining forces with Mr Burnham.

Mrs Badenoch asked: “Does the Prime Minister think that his treachery should be rewarded by being appointed Chancellor?”

There will be Labour MPs asking the same question.

Andy Burnham will be making a huge mistake if he gives Ed Miliband the Treasury job. By making this crystal clear, Mrs Badenoch may even have done Mr Burnham a favour.