Diane Abbott once made the case that Chairman Mao did more "good than harm" during a debate over who was the history's worst dictator.
In a clip unearthed and tweeted out by the programme in the early hours of this morning, Abbott spars with Portillo and Neil over just how bad the communist Chinese leader was.
This Wednesday, Labour was engulfed in a bizarre row over Mao, after shadow chancellor John McDonnell decided to quote from his Little Red Book in the Commons.
On This Week, Neil wondered why it was seen as ok to wear a t-shirt with a picture of Mao but not one of Hitler.
"I suppose some people will judge that on balance Mao did more good than harm. You can't say that about the Nazis," she said.
Portillo reacted in surprise, slapping Abbott's leg. "What. You can not be serious Diane," he said. "What was the good he did that made up for the 60 million people he murdered?"
Neil chipped in: "Mao killed tens of millions of people."
Abbott said: "He led his country from feudalism he helped to defeat the Japanese and he left his country on the verge of the great economic success they are having now.
She added: "I was just putting the case for Mao."