Kwasi Kwarteng has blamed Liz Truss for going too fast with her economic agenda and says he warned her she would only last two months if she continued.
The former chancellor says he told Ms Truss to "slow down" and take a "methodical and strategic approach" to growing the economy.
He claims Ms Truss rejected his pleas and that he was forced to warn her "you will have two months if you carry on like this". She managed 44 days.
Speaking to TalkTV in his first interview since he was sacked, Mr Kwarteng said the prime minister - one of his closest friends and political allies - had been "distressed and emotional" when she sacked him.
The former chancellor also defended his mini-budget, saying that Rishi Sunak cannot "simply keep putting up taxes".
However, he admitted that their ambitious blueprint for the economy had been pushed forward too quickly.
Mr Kwarteng told TalkTV: "After the mini-budget we were going at breakneck speed and I said, you know, we should slow down, slow down.
"She said, 'Well, I've only got two years' and I said, 'You will have two months if you carry on like this'. And that is, I'm afraid, what happened."
He added: "I think the prime minister was very much of the view that we needed to move things fast. But I think it was too quick."
Mr Kwarteng's self-confessed radical plan to spark economic growth after more than a decade of stagnation never landed well.
It unleashed a cycle of falling market confidence, flight from British assets and such damage to the bond markets that the Bank of England was forced to intervene and start buying gilts.
Critics said the scrapping of the top rate of income tax, and the removal of a cap on bankers' bonuses, favoured the rich during one of the toughest economic crises in decades.
Days after the plan was unveiled, Mr Kwarteng was forced into a U-turn on income tax.
Mr Kwarteng backed Mr Sunak as a "very credible prime minister" but warned the new administration against blaming him and Ms Truss for the government's current problems.
"The only thing that they could possibly blame us for is the interest rates and interest rates have come down and the gilt rates have come down. I mean, it wasn’t that the national debt was created by Liz Truss’s 44 days in government", he told TalkTV.
He said that he supported the idea that taxes had to rise in the short-term but insisted that it would not grow the economy long-term.
"You’re not going to grow an economy or incentivise economic growth by putting up our taxes," Mr Kwarteng said.
The Treasury has claimed that the mini-budget has left a £50bn black hole in the economy which is forcing it to increase taxes for millions of households.
However, Mr Kwarteng told TalkTV: "The national debt wasn't radically changed by Liz Truss...
"The black hole hasn't been caused by the mini-budget. And I think it's something that Jeremy (Hunt) and Rishi and their officials are going to have to tackle on their own regardless of what happened in the budget."
Speaking of his dismissal by Ms Truss, Mr Kwarteng said he first learned of his firing via a tweet as he travelled to a meeting with Ms Truss in Downing Street.
Ms Truss sacked him on October 14 after he had been in Number 11 for just six weeks.
He said: "I can’t remember whether she was actually shedding tears but she was very emotional and it was a difficult thing to do. I think she genuinely thought that that was the right thing to buy her more time to set her premiership on the right path."
The pair co-wrote Britannia Unchained in 2012 which argued that the UK was being held back by a "bloated state, high taxes and excessive regulation".
His tenure as chancellor was the shortest since 1970, when Conservative Iain Macleod died one month into the job.
His dismissal only bought Ms Truss limited breathing space. She was forced to resign a week later, going down as the shortest-serving prime minister in history.
