Speaking for the first time since he was ousted by the bank nine months ago in the wake of the Libor rate-rigging scandal, Diamond also questioned whether the Bank of England's governor, Sir Mervyn King, had the authority to force him out of his job last July, days after the bank was fined £290m for rigging Libor.
"This is going to sound arrogant as hell but I never did anything for money. I never set money as a goal. It was a result," Diamond said in an interview with the New York Times magazine to be published on Sunday.
The banker known as Red, after his initials, was at the centre of a row over his £2.7m bonus for 2012 in the months before he quit. The bank was faced with a shareholder rebellion in protest at his proposed payout. Diamond eventually accepted tweaks to the deal in an attempt to head off a major revolt.
Once branded "the unacceptable face of banking" by Lord Mandelson, he told the New York Times, which published pictures of him travelling on the New York subway, that he was not money-motivated, and that he did not have a flash car or any of the other trappings of wealth. Diamond said he only had an old Jeep at his holiday home in Nantucket, near Cape Cod. He also has homes in Beaver Creek, the ski resort in Colorado, and a £25m penthouse apartment on the 40th floor of 15 Central Park West, a New York complex that is also home to pop star Sting and the Goldman Sachs boss Lloyd Blankfein. He bought the apartment under the name Novgorod to avoid his identity being revealed.
Since giving evidence to the Treasury select committee the day after his resignation, Diamond has said little in public, apart from giving the occasional lecture at Yale. However, he reveals that he wants to get back into banking, working with big companies.
In the interview, Diamond recalled how the then Barclays chairman Marcus Agius arrived at his London home on a Monday evening in July to tell him that King wanted him out.
"My first reaction, which is still my reaction today, is, he [King] doesn't have the authority to do that!" Diamond said.
The 61-year-old American-born banker said he discussed the matter with his wife, Jennifer, with whom he has three children, and concluded that the best thing he could do for Barclays was "step aside and shut up".
To underline his claim that he had not worked for money, Diamond, who is also a British citizen, said he had set up a family charity, which supports education projects, after he had started to make money. "If you look at how Jennifer and I and our three kids have lived our lives, as soon as we had any money at all, we created a family foundation … I think Jennifer and I have always had a great home for our kids. We really like to take vacations with them, so those are good. But we don't have a boat, we don't have fancy cars. I think we have lived well, but it hasn't been about accumulation or anything like that."
Shortly after he quit, his daughter Nell tweeted her support, saying: "George Osborne and Ed Miliband you can go ahead and #HMD [hold my dick]". Diamond said she had called him to say she had done "something really bad, I think I'm in trouble", to which he said he replied: "Sweetie, I love you. That's so nice. I think we're probably all in trouble."
He told the New York Times that he did not know much about Libor. "Do you want the truth? Up until all of this, I didn't even know the mechanics of how Libor was set. If you asked me who at Barclays submitted the rate every day, I wouldn't be able to tell you. I bet you if you asked any chief executive of any bank on the street, they would give you the same answer."
Days after Diamond took the top job at Barclays, in January 2011, he stoked anger when he told MPs that the time for bankers to show remorse for the near-collapse of the banking system was over. In the interview he admitted that he had underestimated how he had been perceived in the UK, but insisted that leaving had been "very positive and kind of liberating".
"Do I think I was tone-deaf to the American thing?" he said. "Probably. I think that the anger against banks and bankers, particularly in the UK, was deeper than I realised."
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