Iain Duncan Smith broke down and cried during a television interview about the plight of a single mother he had met.

Duncan Smith was being interviewed by Private Eye editor Ian Hislop for a new BBC documentary on benefits - months before he dramatically resigned as work and pensions secretary - when he was overcome with emotion.

"Sorry - I'm quite emotional," Duncan Smith says with his voice quivering and his eyes filling with tears, as he describes his encounter with a 19-year-old unemployed single mother.

Hislop said it was a "very extraordinary moment".

"It was a curious thing," he told the Radio Times. "IDS actually broke down. He wept in front of me. It was a very extraordinary moment."

Asked whether he attempted to comfort the ex-Conservative leader, Hislop replied: "No, I just watched him cry.

"We're sitting in the Department for Work and Pensions talking about his desire to increase the lot of those without any privileges or start in life and he starts welling up."

The programme 'Workers or Shirkers? Ian Hislop's Victorian Benefits' airs on April 7 on BBC Two.

Duncan Smith resigned from the Cabinet in March, describing planned cuts to disability benefits as "unfair" and "a compromise too far".