Bill Clinton has opened up about his affair with then-White House intern Monica Lewinsky during his time as US President in a new documentary series about his wife Hillary.

The ex-president claimed he had sex with Ms Lewinsky – who was just 22 at the time – to relieve the pressures of the job. He saw his intern as ‘something that will take your mind off it for a while’, he said. Leading the country, he said, makes you feel like ‘you’ve been in a 15 round prize fight that was extended to 30 rounds’. He added: ‘Everybody’s life has pressures and disappointments, terrors, fears of whatever.’

Having an affair, Mr Clinton said, was among ‘things I did to manage my anxieties for years’. Former presidential candidate and secretary of state Mrs Clinton told the documentary she was ‘devastated’ by her husband’s infidelity. ‘I could not believe it. I was so personally just hurt and I can’t believe this, I can’t believe you lied,’ she said.

The four-part series ‘Hillary’ will be available to watch on Hulu from Friday. In one episode of the documentary, focused on the affair, Mr Clinton offers an apology to Ms Lewinsky, who in recent years has begun to publicly speak out about their relationship, saying her view of it changed during the #MeToo movement.

She struggled for years to fight her life being defined by the affair.

The former president said he felt ‘terrible’ that her life had been ‘unfairly’ tainted by it. Both Clintons – who were interviewed separately for the show – reflect on Mr Clinton’s initial lie that he had had sex with his intern, before admitting to the nation that they had in fact had a sexual relationship.

The relationship, and Mr Clinton lying about it during a deposition, led to his impeachment. He was subsequently acquitted by the Senate.

On staying by her husband’s side, former first lady Hillary said: ‘Some people thought I made the right decision and some people thought I made the wrong decision and so I have gotten both affirmation and criticism for the decision I made and that was true from the very beginning of deciding that.’

Mr Clinton ends the episode saying: ‘I was so grateful that she thought we still had enough to stick it out. God knows the burden she paid for that.’ The couple underwent ‘painful’ marriage counselling sessions as a result of the affair, Mrs Clinton said.

Hillary was interviewed for 35 hours for the documentary, alongside many members of her 2016 election campaign staff. She recently told Vanity Fair that she signed up for it ‘because I’m not running for anything’.

‘I felt like if I didn’t tell my side of the story, who would? At least there’ll be a baseline: Here’s what actually happened in my life. Here’s what I actually said about it,’ she said.