The singer's bandmate Geri Horner was famously quoted as saying in a 1996 interview that the Wannabe singers were big fans of the late prime minister.
"We Spice Girls are true Thatcherites," she declared. "Thatcher was the first Spice Girl, the pioneer of our ideology - Girl Power."
But Chisholm, 48, has now revealed that wasn't really the case.
Asked by The Independent if she considered Thatcher to be the OG Spice Girl, she replied: "Absolutely not!”
She went on: "I’m from Liverpool. It was a name that was not celebrated in that region. They were never the thoughts or feelings that I shared.
"People knowing me, from the things I do, are quite aware of what kind of person I am. I don’t think people think I’m a raging Tory!”
Mel – who has gone on to have a solo music career – has been opening up about her time in the group lately, and recently said that she was banned from having a boyfriend while the other band members were free to date.
She told Australia's The Project: "The rule for the other women was, 'She is fine, she can have a boyfriend, she can cope with having a boyfriend, she is strong enough but you are not.'
"It makes you question yourself when you are already vulnerable."
Their hits include Too Much, Say You'll Be There and 2 Become 1.
Watch: Mel C opens up about sexual assault experience