Mr Kwarteng was sacked 38 days into Ms Truss’s short stint as Prime Minister after a package of radical tax cuts, billed as a ‘mini budget’, plunged the financial markets into turmoil.
Speaking about post-office life in an interview with Politico, Mr Kwarteng said he had not spoken with his former long-standing ally about his sacking since it happened.
Ms Truss resigned days after firing her Chancellor, becoming the shortest-serving prime minister in British history.
“I mean, my issue with her was that, having been bold on the entry … for me, it was a total capitulation at the end. And, I think, I felt let down, frankly,” he said.
The former Cabinet minister said that for many people who leave high office, there was a “numbness”.
“You just get these empty, this feeling of kind of emptiness,” he told the publication’s podcast.
“You’ve got to remember that for a lot of people who are right at the top, they’ve been thinking about this for decades.
“They've been on this road, on this journey.
“And then once you're out, it's over. And so there's a kind of feeling of emptiness. I've seen it and you can see it on their faces sometimes. They're just completely bewildered.”
However, he added that he personally “really enjoyed” being Chancellor, saying it was a “great honour”.
Current Chancellor Jeremy Hunt, a former foreign secretary, was parachuted into Number 11 to replace Mr Kwarteng in a bid to restore order to Ms Truss’s ailing administration.
However, Ms Truss resigned days later, saying it was clear she no longer had the confidence of her party - making her the shortest-ever serving PM.
Rishi Sunak took over the top job in October last year, admitting candidly that “mistakes had been made”.
Speaking as he took office, Mr Sunak said the mistakes of the former administration were “not born of ill will, or bad intentions”, but needed fixing nonetheless.