The actor, who grew up in a mining village in Yorkshire under Margaret Thatcher’s government in the Eighties, said some of the things she found out about her family in the BBC genealogy show went against her political beliefs.
On the programme, she learned that her great-grandfather was a strike breaker in the 1920s.
Speaking to Radio Times, she said: “As I understand it, it's their colliery and they're working through the strike… It's not an ideal bit of your family history. Essentially they were scabs.
“Living here during the Eighties, the idea that you work through a strike feels like it goes against everything you are brought up to believe in.”
Whittaker’s great-grandfather began working in the mines at just eight years old, but within 20 years was effectively running his own mine with his sons.
During the National Coal Strike of 1921 and the General Strike of 1926, when most miners were refusing to work, he kept his mine open and earned a small fortune.
In the show, Whittaker said: “There’s a way of looking at this that is just filled with pride because a man bettered himself and then his entire family, and that family took on that work ethic of grafting and took it to another level. [They] built up this successful business that then looked after generations of the family. That is a huge success from [being] an eight-year-old miner.
“But the problem is when it comes at a cost. On your doorstep, there must have been enough families that you saw sacrificing so much just to try and have their basic rights.”
She said that part of her family’s history makes her feel “uncomfortable” because of her left-leaning politics.
Who Do You Think You Are? series 17 airs at 9pm on Monday 12 October on BBC One.