Prince Harry, Meghan Markle 'cheapening' the royal family - Thomas Markle

Meghan Markle's estranged father has accused Prince Harry and his daughter of "cheapening" the monarchy in their bid to "carve a progressive new role" as financially independent royals.

Thomas Markle, 75, has revealed his thoughts on the Megxit controversy in an upcoming Channel 5 documentary, Thomas Markle: My Story.

In the exclusive interview, Markle addressed Meghan and Harry's decision to step back as senior royals and split their time between Britain and North America.

"They are turning [the royal family] into a Walmart with a crown on," Markle said.

"When they got married they took on an obligation, and the obligation is to be part of the royals and to represent the royals… 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."

Markle's "complicated" relationship with his daughter reached breaking point prior to her 2018 wedding to Harry. The 75-year-old, who missed the nuptials due to heart surgery, said he can't see his daughter "reaching out" anytime soon.

"I think both of them are turning into lost souls at this point... I don't know what they're looking for," he said.

"It's disappointing because she actually got every girl's dream."

The retired Hollywood lighting director also spoke of the couple's refurbished family home, Frogmore Cottage, saying it's "embarrassing" that the US$3 million, 26-room home "isn't enough for them".

Harry and Meghan have agreed to repay the taxpayer-funded $4.7 million refurbishment of Frogmore Cottage as part of their new arrangement with Queen Elizabeth II, which was announced on Saturday (local time).

As of autumn [NZ time], the Sussexes will no longer carry out royal duties and will be permitted to generate income through their own means. Although they will maintain their private patronages and associations, Harry will step back from his military appointments and will no longer be paid for public duties. They will no longer be referred to as "His Royal Highness" or "Her Royal Highness".

As part of the deal, Harry and Meghan will also be allowed to strike commercial deals through their Sussex Royal brand. According to the Daily Mail, experts estimate the brand could be worth at least £400 million (NZ$787 million).

"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," Thomas claimed.

Despite the Queen calling the arrangement "constructive and supportive" in a statement, UK press claim the monarch remains "privately unhappy" with her grandson and Meghan's decision.

The Channel 5 documentary will reportedly explore Markle and Meghan's relationship, including her formative years with her father and the dramatic fallout ahead of her wedding to Prince Harry. A release date has not been announced.