When Oprah quizzed the Sussexes for more information, they refused to say who said it to Harry as it was “too damaging to them."
Harry adamantly told Oprah: "That conversation, I'm never going to share.”
Responding to the bombshell accusations, Piers later accused the Sussexes of trashing the entire royal family, explaining their omission was far worse than calling out an individual.
"As for the racism claims, if this happened we need names or everyone there gets smeared with the same terrible charge,” Piers tweeted following the interview.
He then went on a rant on live television, in which he questioned why Harry for discussing every other subject but staying silent on the racial claim about dropping the bombshell.
"They trash everybody. They basically make out that the Royal Family are a bunch of white supremacists, by dropping this [racism] bombshell,” Piers told viewers on Monday.
"They didn't name anyone. They just throw it out there, it could be any member of the Royal Family, they didn't name which one it was, and Harry says: 'I'll never say who it was', well you better say it fast.
"It's odd though because [Harry] was comfortable sharing everything else in that interview, but [he] was prepared to just let that bombshell lie just completely unanswered, so we now have to think it could be any one of the Royal Family that was apparently racist about the skin colour of your child.
"I don't think that's acceptable," he added.