Speaking on his way to the COP27 climate summit in Egypt, Mr Sunak said he supported the chief whip’s decision to suspend Mr Hancock from the Conservative Party, adding that he would not have time to watch the ITV reality show.
The MP for West Suffolk faced heavy criticism when it was announced he was going on the show.But he defended his decision saying he wanted to "go where the people are" rather than "sit in ivory towers in Westminster".
The PM joined in the criticism on Sunday, telling The Sun "MPs should be working hard for their constituents".
Mr Sunak said: "I think politics is a noble profession, at its best – it can and should be – but it’s incumbent on politicians to earn people’s respect and trust.
"They do that by working hard for their constituents, as the vast majority of MPs do – that is why I was very disappointed with Matt’s decision."
When asked whether he would be watching the programme, Mr Sunak told the newspaper: "I genuinely won’t have the time, is the honest answer."
The latest series kicked off on Sunday with 10 celebrities making an appearance. It is expected Mr Hancock will join in the next few days.
In an opening monologue, host Ant McPartlin hinted at Mr Hancock's arrival.
He said: “We have not one but two late arrivals on the way.
"And fortunately we have managed to keep their identities a complete secret. No-one has got a clue who they are."
Stressing the word "mat", Declan Donnelly added: "You are going to be surprised, guys. We are going to be rolling out the welcome mat for them soon."
Meanwhile, Business Secretary Grant Shapps said he will not be voting for Mr Hancock on the show and that he thinks his fellow Tory MP should be here “looking after his constituents”.
Asked if he was looking forward to seeing the 44-year-old having to eat crocodile anus, Mr Shapps told Sky News: “Tempting as that is, I think I’ll probably be focusing on my job as Business Secretary, and I’ll be off at Cop27 later this week as well, so I fear I might miss him depending on how long he survives.”
He said he will not be voting for Mr Hancock to compete in the reality show’s gruelling challenges, adding: “I just think he should be here looking after his constituents, rather than in the jungle somewhere.
“So, no, I won’t be. I won’t be voting for him. I can’t promise I’ll be voting for anyone at all. So that might just be (by) omission rather than anything else.”
Responding to criticism, Mr Hancock previously told The Sun he wants to use the "incredible platform" on the show to raise awareness of dyslexia and insisted it "wasn’t the cheque" that made him decide to join the programme.
Leading figures at organisations specialising in dyslexia have said they are grateful to the former cabinet minister for his work raising awareness of the learning difficulty and welcomed a platform for the cause.
But in his own constituency, many have not taken the news well.
Discussing Hancock’s upcoming appearance, Andy Drummond, who is chairman of Newmarket Conservatives and deputy chairman (political) of West Suffolk Conservative Association, said: "I’m looking forward to him eating a kangaroo’s penis.
"Quote me. You can quote me that."
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