Thomas Markle has accused his daughter of "cheapening" the royal family.
The 75-year-old director of photography has spoken out about Meghan Markle and Prince Harry's decision to quit as members of the royal family, saying the loved-up couple are "turning into lost souls".
Speaking to Channel 5 in a new TV documentary, he explained: "They are turning it [the royal family] into a Walmart with a crown on."
Thomas described the royal family as "one of the greatest long-living institutions ever".
However, he accused his daughter and Prince Harry - who are parents to eight-month-old son Archie - of making the royal institution appear "shabby".
In the new documentary, titled 'Thomas Markle: My Story', he says: "When they got married they took on an obligation, and the obligation is to be part of the royals and to represent the royals. And it would be foolish for them not to.
"This is one of the greatest long-living institutions ever. They are destroying it, they are cheapening it, making it shabby ... they shouldn't be doing this."
Thomas also claimed his daughter has turned her back on "every girl's dream" by deciding to distance herself from the royals.
He said: "With Meghan and Harry separating from the royals ... it's disappointing because she actually got every girl's dream.
"Every young girl wants to become a princess and she got that and now she's tossing that away ... it looks like she's tossing that away for money."
And speaking in reference to their refurbished home, Frogmore Cottage near Windsor Castle, Thomas added: "Apparently $3 million and a 26-room home isn't enough for them ... it is kind of embarrassing to me."
Harry and Meghan - who have been married since May 2018 - have agreed to relinquish their public funding and repay the cost of the refurbishment work on their home.