During an interview with GBNews in the UK, Thomas Markle unleashed a series of bizarre comments about his son-in-law Prince Harry, including implying that there is something wrong with him mentally.
In a clip shared by GBNews, Thomas Markle pulls no punches as he accuses his daughter Meghan and her husband Harry of having "harmed so many people".
"They've gone out of their way to harm people," continues Markle, accusing them of harming the royal family, his family and all of Britain, "I don't know what's wrong with them."
When asked by GBNews journalist, Dan Wootton, if he thought the term 'Megxit' was sexist, Markle said no and attributed it to Harry's "ignorance".
"Maybe he was dropped on his head as a baby," Markle remarked, before continuing: "Everything that comes out of his mouth is always kind of stupid.
"He rides a bicycle every day around where he lives. I understand they are going to take the training wheels off soon."
In a separate clip, also shared by GBNews, Thomas Markle discusses the infamous letter that he received from Meghan after her wedding to Harry, which her father didn't attend.
Markle famously shared the 'Daddy letter' with the Mail on Sunday and the very personal contents were shared around the world.
When Wootton suggested that either the Queen or Prince Charles were likely to have instructed Meghan to write the letter, Markle was quick to defend them.
"I have the greatest respect for the Queen and for the royal family, especially the Queen. I don't think she would ever recommend anyone to write a letter like I received."
Meghan successfully sued Publisher Associated Newspapers for invasion of privacy and copyright infringement for their printing of excerpts of the private letter in the Mail on Sunday and on the MailOnline website.
A High Court judge sided with Meghan in February, ruling that the paper's publication of the letter was "manifestly excessive and hence unlawful".
The publisher is now appealing against the judge's ruling and is trying to assert that the Duchess of Sussex knew the letter she sent to her father, Thomas, would potentially be published.