Former prime minister David Cameron in a candid interview with The Times revealed that he thinks about the Brexit referendum "every single day."

In a new book, the former prime minister said during the referendum campaign cabinet colleagues and Leave campaigners Boris Johnson and Michael Gove behaved "appallingly."

The UK voted 52% to 48% to leave the EU in the June 2016 referendum.

Boris Johnson, the current prime minister, has pledged to leave the EU with or without a deal by the October 31 deadline.

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Former British prime minister David Cameron has revealed that he thinks about the Brexit referendum "every single day" and attacked Leave campaigners Boris Johnson and Michael Gove for behaving "appallingly."

Cameron, who stepped down as prime minister after campaigning to remain in the EU in the 2016 referendum and losing, told The Times the result had left him feeling "hugely depressed."

"I think about this every day. Every single day I think about it, the referendum and the fact that we lost and the consequences and the things that could have been done differently, and I worry desperately about what is going to happen next," said Cameron. "I think we can get to a situation where we leave but we are friends, neighbours and partners. We can get there, but I would love to fast-forward to that moment because it's painful for the country and it's painful to watch."

When asked whether he has trouble sleeping, he replied "I worry about it a lot. I worry about it a lot."

However he defended his 2013 pledge to hold a referendum if the Conservatives won the forthcoming general election. After winning a parliamentary majority in the 2015 general election, Cameron made good on the pledge.

"As I say, when I think through all the things I thought and all the arguments I had with colleagues and with myself, I still come to the same conclusion: that we were going to have a referendum," he said.

Cameron has kept a low-profile since stepping down as prime minister, but has broken his silence with the release of a new book. In the book, Cameron criticizes former party colleagues Boris Johnson and Michael Gove, who led the Leave campaign, writing that they behaved "appallingly."

He further described his dismay at their behaviour in the campaign in the interview with The Times.

"Boris had never argued for leaving the EU, right? Michael was a very strong Eurosceptic, but someone whom I'd known as this liberal, compassionate, rational Conservative ended up making arguments about Turkey [joining] and being swamped and what have you. They were trashing the government of which they were a part, effectively."

He described the claim of the two Leave campaigners during the referendum that Turkey could be poised to join the EU as "ridiculous."

"I suppose some people would say all is fair in love and war and political campaigns. I thought there were places Conservatives wouldn't go against each other. And they did," remarked Cameron.

Of Gove, he said the friendship they had formed at university had been damaged by campaign.

"We've spoken. Not a huge amount," Cameron said. "I've sort of had a conversation with him. I've spoken to the prime minister a little bit, mainly through texts, but Michael was a very good friend. So that has been more difficult."

During the campaign Cameron argued that Britain's economic prosperity would be damaged by leaving the EU.

"I loved the explaining and arguing and that side of politics, persuasion, but then, as it went on, I just felt more and more bogged down. It turned into this terrible Tory psychodrama and I couldn't seem to get through," said Cameron. "What Boris and Michael Gove were doing was more exciting than the issues I was trying to get across. I felt like I was in a sort of quagmire by the end."

Theresa May was chosen by Conservative MPs to lead the party after Cameron's departure, but a deal she struck with the EU to leave the union was opposed by MPs including hardliners in her own party, and she stepped aside in June.

Her successor, Johnson, has pledged to leave the EU by the October 31 deadline with or without a deal, despite MPs recently passing legislation to block a no deal Brexit.

Cameron in the interview said he hopes Johnson succeeds as prime minister, but was critical of his recent moves.

In seeking to force Brexit Johnson has prorogued parliament and ousted moderate MPs from the conservatives opposed to no deal, including two former chancellors and the grandson of Winston Churchill.

"Taking the whip from hard-working Conservative MPs and sharp practices using prorogation of Parliament have rebounded," he said.

"I didn't support either of those things. Neither do I think a no-deal Brexit is a good idea."

In the interview, he didn't rule out the possibility of a second referendum to end the parliamentary impasse.

"I don't think you can rule it out because we're stuck," he said.

"I'm not saying one will happen or should happen. I'm just saying that you can't rule things out right now because you've got to find some way of unblocking the blockage."