Omid Scobie, the author of a biography the Sussexes authorised staff to cooperate with, said: “There’s been rumours that a lot of the most damaging and negative stories about Harry and Meghan that have appeared in the press have come from other royal households or other royal aides or courtiers.

“And from my own reporting that is exactly true.”

The first episode of The Princes and the Press, which was aired on Monday night, detailed the media coverage of younger members of the Royal family from the Queen’s Diamond Jubilee in 2012, when the Duke and Duchess of Cambridge and Prince Harry were considered the bright future of the monarchy.

It tracked positive media coverage up to and around Prince Harry’s wedding to Meghan Markle in 2018, and explores the Princes’ relationship with the press including phone hacking.

The second episode, due for broadcast on November 29, is expected to go through some of the key newspaper stories uncovering fractured relationships behind closed doors, with allegations of palace insiders briefing the media.

Much of it was filmed many months ago, and edited at the last minute after it needed to be updated with details of the Duchess of Sussex’s court case against the Mail on Sunday.

In a trailer for the accompanying podcast, Rajan said he wanted viewers to question how they had formed opinions on the Duke and Duchess of Sussex based on the media lens they are reported through.

A source said the programme is intended as a “cerebral” look at the palace and press and was not intended to be “incendiary”.

The three households of the Queen, the Prince of Wales and Duke of Cambridge have united to complain to the corporation about its lack of transparency about what is in the documentary.

No previews were available before the programme aired on Monday night, with next week’s episode expected to air allegations that the palace have never previously given enough credence to to comment.

A BBC spokeswoman said: “The programme is about how royal journalism is done and features a range of journalists from broadcast and the newspaper industry.”

BBC guidelines require all news and current affairs documentaries to offer “right of reply” to anyone implicated in their journalism.

A joint statement from Buckingham Palace, Clarence House and Kensington Palace said: “A free, responsible and open press is of vital importance to a healthy democracy.

“However, too often overblown and unfounded claims from unnamed sources are presented as facts and it is disappointing when anyone, including the BBC, gives them credibility.”