Two months on and ahead of the documentary being broadcast, Mrs Duncan's comments have been revealed. She was filmed telling Ukip press officer Liz Langton Way: "The only people I do have problems with are n-----s. And I don't know why.
"I don't know whether there is something in my psyche or whether it's karma from a previous life or whether something happened to me as a very, very young person and I've drawn a veil over it - because that sometimes happens, doesn't it?"
Mrs Duncan, who remains an independent councillor in Thanet, has since said she does not believe the comments were "racist or derogatory".
"I used the word ' n-----s' as you would do Asians, Chinese, Muslims, Jews. It's a description, it's not an insult - in the same way as you would say, 'What do you mean by Jewish? Well, they belong to a community, they have got a certain faith, they have usually got noses that have got a bit of a curve to them, married women - if they are orthodox Jews - wear wigs.' It's description."
You can see the video below, but be warned it does feature racially offensive language.
Meet the Ukippers is on BBC Two at 10:00pm on Sunday 22 February