Mr Kwarteng, who was sacked 38 days into Ms Truss's short-lived tenure as prime minister, also revealed the pair had not spoken since she dramatically sacked him following his mini-budget last September, which sent the pound tumbling and unleashed chaos in the markets.

Ms Truss resigned days later, becoming the shortest-serving prime minister in British history.

Mr Kwarteng and Ms Truss had been longstanding allies before she sacked him following criticism of the tax-cutting measures in the mini-budget, replacing him with the incumbent chancellor, Jeremy Hunt, who unpicked her agenda to restore faith in the markets.

As well as both occupying Number 10 and Number 11 Downing Street, Ms Truss and Mr Kwarteng are still thought to live in Greenwich in nearby streets. The pair struck up their friendship after entering parliament together in 2010.

In an interview with POLITICO, the former chancellor said his "issue" with Ms Truss 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."

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The former cabinet minister, who represents Spelthorne, also described how many senior politicians feel a sense of "numbness" and "emptiness" after leaving high office.

"These people, political people, but I think particularly people who get to the top, they're kind of adrenaline junkies," he told the Westminster Insider podcast.

"They enjoy the challenge. It's like watching or being involved in a kind of action movie yourself. Not to trivialize it, but, you know, you're right at the center of events, you've got a lot of authority. You get to decide things."

He went on to describe a "kind of emptiness" for some who leave top government roles.

"You just get these empty, this feeling of kind of emptiness," he said.

"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."

When asked if he felt the same way, Mr Kwarteng said he "really enjoyed" serving at the top despite it being "very nerve-racking as well".

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But he added: "I've always tried to be a bit more balanced."

Mr Kwarteng's intervention comes just days after the anniversary of when Ms Truss first took office.

In previous interviews, the former chancellor has expressed regret at the approach the pair took towards their economic agenda, telling the FT Weekend magazine last December that they "blew it" and got "carried away" with bringing in sweeping economic reforms.

The Tory MP said the low-tax, small-state plans they had were "very exciting" and he was fully behind them but accepted that the way they were executed led to their downfall.

In some of her speeches since leaving Number 10, the former prime minister defended her tax-cutting agenda and suggested it would have worked out in the long term.

At the launch of her Growth Commission in July - a new organisation she set up to bring together economists focused on the issue of low growth - she suggested the UK's sluggish growth had "got worse" following her exit.

The former prime minister was overheard at the event saying it hadn't "dramatically gone away" with her exit from Downing Street, but "got worse and worse".

When asked if her fiscal plans had been the right one, she replied: "It's a long game."