Keir Starmer's true colours were exposed as he made a surprise appearance on Tuesday's instalment (October 15) of BBC Breakfast.
The Prime Minister was interviewed by BBC political correspondent Henry Zeffman, which led to fans switching off the programme.
During the interview, Sir Keir warned that October 30 would bring a "tough" budget amid speculation that Chancellor Rachel Reeves could announce more tax rises than those included in Labour's manifesto.
However, he denied Labour will be breaking promises to voters by hiking employer national insurance contributions. Body language expert Judi James looked into the politician's behaviour during the interview, suggesting there were moments where he felt "unhappy" and exhibited "stubbornness".
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Judi said: "Starmer's very emphatic pose here would define the word 'Look...' that political leaders employ before they either lay out a challenging point or before they swerve a question altogether.
"His brows are raised in emphasis and the raising of the brows widens the eyes which would traditionally suggest some sense of surprise but also a desire to look open."
She continued: "He has both his hands in a 'digging' position with the thumbs partly cocked. When the thumbs are fully cocked they signal total confidence and enjoyment in the communication. These don't quite get there though, hinting he's not overly happy to be explaining himself here.
"The 'digging' angle of the hands suggests some stubbornness though, as though he will make some effort to persuade, explain or sell his point but in reality he'll be doing whatever it is anyway."
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Asked whether the Labour manifesto ruled out any increase in National Insurance during the interview, the Prime Minister said: “We were very clear in the manifesto that we wouldn't be increasing tax on working people. And we expressly said that that was income tax, that was NICs, etc.”
Pressed on whether this included employer contributions, Sir Keir esponded: "It's very clear from the manifesto that what we were saying is we're not going to raise tax for working people, and it wasn't just the manifesto.
“We said it repeatedly in the campaign, and we intend to keep the promises that we made in our manifesto. I'm not going to reveal to you the details of the budget."
After insisting Labour would not be breaking promises in their manifesto, he added: "The focus will be on rebuilding our country, and ensuring that we get the growth we need in our economy and so it's consistent with the summit we had yesterday."
