Norway's Princess Martha Louise on Tuesday relinquished her royal duties in order to focus on her alternative medicine business with her fiance, a self-proclaimed shaman.

The 51-year-old princess' relationship with Durek Verrett, a popular Hollywood spiritual guru, caused waves in Norway after the African-American "sixth-generation shaman" suggested in his book "Spirit Hacking" that cancer was a choice.

He also sells a $222 medallion on his website dubbed a "Spirit Optimizer", which he claims helped him overcome Covid-19.

A poll in September found 17 percent of Norwegians now have a lower opinion of the generally popular royal family, nearly all citing the princess and the shaman as the reason.

In a video posted to Instagram on Tuesday, the princess said she was stepping down "in order to bring calm to the Royal House".

The palace said the princess was "relinquishing the role as royal patron... and will not be representing the royal house at the present time".

However, "in accordance with the king's wishes, the princess will keep her title".

King Harald, speaking to the press later with Queen Sonja by his side, said he was "sorry" the princess would no longer represent the royal family.

"She's very good at it," he said.

- 'Agreed to disagree' -

Martha Louise, who claims to be able to speak with angels, lost her honorific "Her Royal Highness" title in 2002 when she chose to work as a clairvoyant.

In 2019, the divorced mother of three agreed not to use her title as princess in her commercial endeavours.

But since becoming engaged to Verrett in June, the couple's belief in alternative therapies, often featured on their social media channels, has raised eyebrows in no-nonsense Norway.

Several groups of healthcare professionals had already dropped the princess as a patron because of her fiance's penchant for alternative medicine.

"He's an imposter, a charlatan and a quack," columnist and humourist Dagfinn Nordbo has said.

According to the agreement announced Tuesday, the couple will refrain from any association with the royal family in their social media channels, media productions and commercial activities.

"This is intended to draw a dividing line that more clearly separates commercial activity from the Royal House of Norway", the palace said.

Speaking of Verrett, the king told reporters that following discussions between all parties, "both we and he have a greater understanding of what this is all about, and we've agreed to disagree".

"We can live with our differences", he added.

- 'Spirituality important' -

The royal family said it had "great confidence in the Norwegian health service and the Norwegian health authorities", stressing the importance of "established medical knowledge and scientific research".

Martha Louise said she was "aware of the importance of research-based knowledge".

"I also believe, however, that there are components of a good life and sound physical and mental health that may not be so easy to sum up in a research report."

She said "spirituality, intimacy with other people and animals, yoga and meditation" could be important supplements, as could "a warm hand, an acupuncture needle, a crystal".

It was key "to distinguish between myself as a private person on the one hand and as a member of the royal family on the other", she said.

She hoped her personal views would be treated as her own "without others having to answer for them".

The king said he thought Verrett -- whom he described as "a great guy and very funny" -- also now had a better understanding of the role of the monarchy in Norway.

"Americans don't understand the meaning of it. They don't," he said with a laugh.

The palace said that once the princess and Verrett were wed, her new husband would become a member of the royal family but would not hold a title or represent the monarchy.