Prince Harry and Meghan Markle's calls to Americans to "reject hate speech" and vote ahead of the country's upcoming presidential election has "violated" the couple's Megxit deal with the Queen, according to senior royal aides.
The Duke and Duchess of Sussex made the comments in a live, televised broadcast earlier this week as part of the Time 100, a list compiled by Time magazine in celebration of the world's most influential people.
"As we approach this November, it's vital that we reject hate speech, misinformation and online negativity," Harry said.
He also encouraged Americans to be selective in the content they consume online.
"When the bad outweighs the good, for many, whether we realise it or not, it erodes our ability to have compassion and our ability to put ourself in someone else's shoes," he said.
"Because when one person buys into negativity online, the effects are felt exponentially. It's time to not only reflect but act."
A royal aide who spoke to the UK's The Sunday Times said the comments broke protocols set under the Sandringham accord - the document that was created after the Sussexes resigned as working royals.
Members of the royal family are supposed to be politically neutral, and according to The Times the pair pledged that "everything they do will uphold the values of Her Majesty". But the aide said the comments have broken that promise.
"The [royal] family are all wringing their hands, thinking: where is this going and does this abide by the deal to uphold the values of the Queen? The feeling is it's a violation of the agreement."
The source said if there has been a violation, Harry's hopes of returning to the Royal Marines and other military positions could be under threat.
He stepped down as captain-general of the Royal Marines as part of the Megxit deal, but The Times said the Queen agreed to keep the positions open during a year-long review period so he could return.
"There were some things that Harry hoped he could opt back into. He dearly wants to hang on to the Royal Marines and the military appointments. That will be harder now."
Another royal aide said courtiers discussed last week whether Harry and Meghan could have their His and Her Royal Highness titles stripped. They still have these titles but aren't allowed to use them.
The source said Harry's title couldn't be removed because even King Edward VIII kept his title after he abdicated.
"[But] there is a strong view that the family really does need to put more distance between them and Harry and Meghan."
Although Harry and Meghan's comments didn't explicitly reference a particular party or presidential candidate, commentators have noted his references are those typically levelled at the Trump administration.
Calling out "hate speech, misinformation and online negativity" - with Trump's tweets frequently flagged by Twitter for violating its policies - has led to the Duke's message being widely interpreted as politically biased, BBC News royal correspondent Sarah Campbell acknowledged in an analysis.
Speaking at a news conference on Wednesday (local time), US President Donald Trump addressed the Sussexes' comments with a bizarre attack on the couple.
"I'm not a fan of [Markle], and would say this... I wish a lot of luck to Harry, because he's going to need it," he responded after being asked about the Duchess.
A spokesperson for the Sussexes said the comments didn't refer to "any specific political party or candidate". They said the remarks were instead "a call for decency in how we engage with each other, interact, and consume information - especially online".