The trailer for the latest episodes of the docuseries on Prince Harry and his wife Meghan was released on Monday, with the royal feud set to escalate with a claim that Buckingham Palace was "happy to lie" for his brother William.

Meghan, 41, separately claims she was "fed to the wolves" after the pair quit royal life in early 2020 and moved to North America

In one excerpt, Harry, 38, accuses Buckingham Palace of "institutional gaslighting" and said "they" were "happy to lie to protect my brother but were never willing to tell the truth to protect us".

The first three episodes of "Harry & Meghan" were released last Thursday, with the couple -- also known as the Duke and Duchess of Sussex -- criticising the royal family for failing to protect her and his mother Diana against tabloid excesses.

Most of the accusations were against the media and the palace press operation, although the couple did direct several barbs against the royal family, including of unconscious racial bias.

Direct mention of Harry's brother, heir to the throne Prince William, 40, in the latest trailer confirmed suspicions that more pointed criticisms may have been saved for last.

"As we all suspected last week, the gloves are off," wrote Daily Mail royal correspondent Rebecca English while her counterpart at ITV, Chris Ship, said: "It's getting dirty".

Harry in late 2019 all but confirmed a rift with his older brother and the pair have reportedly hardly spoken since, even at the unveiling of a statue of their mother last year and the September state funeral of their grandmother, Queen Elizabeth II.

"In previous trailers, Harry has spoken about a 'dirty game' and 'planting' stories," ITV's Ship assessed.

"This clip suggests he is going to blame his brother, or at least the people around him, for some of the stories about the Sussexes which appeared in the press. That is a dramatic escalation."

So far the palace has declined to respond to the programme but commentators suggested it may be forced to if criticism gets personal.