Stanley Johnson told LBC radio on Monday that the questions asked were "disgusting" and said Mair should have been more respectful of his son's position.
"The more I think about it, more I think what a travesty that interview was, not of Boris, but of broadcasting standards," he said.
"I thought Eddie Mair's interview was one of the most disgusting piece of journalism I've listened to for a very long time. The BBC sank about as low as it could.
"His grilling people about their personal lives, accusing them of guilt by association, openly abusing them in a legitimate interview. Frankly, I don't know where we are coming to.
"I have no idea who Eddie Mair is or what he does. But frankly, there is such a thing as respecting the office, even if you don't respect the man and that did not come through."
Johnson was asked about a time he made up quotes while at The Times, and quizzed on why he allegedly "lied" about having an affair to the then Conservative leader Michael Howard.
He was also asked to talk about an infamous phone call between him and his former Eton friend Darius Guppy, recorded in 1990, where Guppy asks Johnson to find the address of a News of the World journalist who has upset him. Despite Guppy's apparent plans, the journalist was never attacked.
"What does that say about you?" Mair asked. "Making up quotes, lying to your party leader, being part of someone being assaulted – you're a nasty piece of work."