Mr Kwarteng believes that Ms Truss only bought herself “a few weeks” left in the job by forcing him out, according to a source quoted in The Times.
The chancellor learnt he was being sacked after reading about in The Times, the paper reported.
He had flown back early from the talks at the International Monetary Fund in America to be told by Ms Truss that he would have to step aside.
“Kwasi thinks it only buys her a few more weeks,” a source told the paper.
“His view is that the wagons are still going to circle.”
One Whitehall source added: “Senior civil servants are now openly talking about her going. They think she’s had it.”
Ms Truss reportedly found it hard to sack her ideological ally Mr Kwarteng but felt it had to be done.
She called the new chancellor Jeremy Hunt at 9:30am on Friday to offer him the job. Mr Hunt, who was on holiday with his family in Belgium, took the Eurostar back to London and arrived back in the UK after 1pm, the paper reported.
The draft forecasts from the Office for Budget Responsibility were reportedly the catalyst for Ms Truss’s drastic shake-up.
The predictions are said to be “dire” and forecast a £60billion short fall in public finances by 2026-27.
In a bid to save her premiership, Ms Truss gave an eight-minute press conference on Friday, in which she took just four questions.
One former minister told The Independent: “She made Theresa May look like Barack Obama. She can’t communicate. She’s just not up to it.”
Another minister said: “She looked like she had been dragged there like a reluctant child being forced to explain itself. There was no contrition.”