If those who believe there will be a Labour-led coalition or a minority government are added to that 65%, the total number who think the opposition will be in power in some form rises up to 87% of the total 861 panel members who replied to the survey.
The panel said this means expectations of a Labour victory are at their highest yet.
Just 13% of respondents said they still have faith that the Tories can clinch another majority term in Downing Street.
The numbers are the exact inverse of the stats ConservativeHome uncovered back in February 2021, when 87% thought the Tories would still lead the government after the next general election.
That survey was conducted at the height of the pandemic and a few months before the partygate scandal was revealed.
In fact, for most of 2020 and into the early months of 2021, more than 80% of responding party members told ConservativeHome they believed there would still be a Tory-led government after the public headed to the ballot box.
So this latest survey is another upset in a long line of negative headlines for Sunak.
Earlier this week, he agreed to a £1,000 bet with Piers Morgan on Rwanda flights taking off before the next election and he made an anti-trans joke in the Commons in front of Brianna Ghey’s mother – both incidents triggered an intense wave of criticism.
Meanwhile, the latest polls from the general public have revealed Labour is still at least 20 points ahead of the Conservatives.
As Kieran Pedley of polling firm Ipsos UK told HuffPost UK, the Conservatives are “running out of time” to change their fortunes.
He said: “Around seven in 10 voters tell us it’s time for a change at the next election. What they’ve got to do is change people’s minds about it being time for a change, which is not an easy thing to do.”