The first three episodes of a docuseries on Prince Harry and his wife Meghan air on Thursday, with expectations of more damaging claims about British royal family life.

The six-part fly-on-the-wall documentary, "Harry and Meghan", promises to lift the lid on events that prompted the pair to quit royal life and move to the United States in 2020.

Trailers aired in the run-up to the much-hyped Netflix release suggest it will further deepen the couple's rift with Harry's family since their acrimonious departure dubbed "Megxit".

One British newspaper said the royal family were viewing the series as a "declaration of war" on the back of the content of promotional clips.

In one, Harry, 38, appears to accuse some within the royal household of leaking and planting stories about the couple in the British press, calling it "a dirty game".

"No one sees what's going on behind closed doors," the prince says. "We know the full truth," he adds in another clip.

"When the stakes are this high, doesn't it make sense to hear our story from us?" Meghan chips in.

The US streaming giant vows it will be "an unprecedented and in-depth documentary series".

The final three parts are to be released on December 15.

"It's seriously threatening... the royal family," commentator Richard Fitzwilliams said of the docuseries, branding it "a form of revenge".

"It could be explosive," he said, adding: "It's very difficult to know what the royal family can do about it."

Netflix showcased the first trailer last week, just as Harry's brother William made his first trip to the US as Prince of Wales and heir to the throne, prompting accusations of sabotage.

The timing could barely have been worse for William after Buckingham Palace sacked one of his godmothers as a courtier for using racially charged language to a black British woman at a reception.

For some, the incident reinforced incendiary claims by Meghan, 41, a mixed-race former television actor, that racism within the royal household was one of the reasons for leaving. (AFP)