"The Times" newspaper reported that the complaint was made in October 2018 by Jason Knauf, who was then the communications secretary for the Duke and Duchess of Sussex at the time.

The complaint claimed the former American actress had allegedly driven two personal assistants out of the household and was undermining the confidence of a third staff member, the newspaper report said.

"The Duchess is saddened by this latest attack on her character, particularly as someone who has been the target of bullying herself and is deeply committed to supporting those who have experienced pain and trauma,” said a spokesperson for Markle, 39, who is now based in California and expecting her second child with Harry, 36.

"She is determined to continue her work building compassion around the world and will keep striving to set an example for doing what is right and doing what is good," the spokesperson said.

Markle lived at Kensington Palace for nearly a year after her marriage to Prince Harry in May 2018. Lawyers for the couple, who stepped back as frontline royals last year, told the newspaper they are the victims of a calculated smear campaign based on "misleading and harmful misinformation".

The development comes as an interview by the couple with American chat show host Oprah Winfrey is due to be aired over the weekend, with clips showing Harry speak about his late mother, Diana – the Princess of Wales, saying he feared history was "repeating itself" before he and Meghan decided to step back as senior royals.

Princess Diana had died in a car crash in Paris in 1997.