Samantha Markle has launched a fresh attack on her half-sister, the Duchess of Sussex.
The 53-year-old criticised Meghan for being "inhumane" to their father Thomas Markle who had "given her everything". She said Meghan should "bow to the daddy".
Samantha wrote on Twitter: "I am not candy coating anything anymore! The DUCHASS should be humane to our father who has given her everything... and this media crap can stop!
"He was the one who was always there for her. Fake waves and smiles can stop. The duchASS can bow to the daddy.
"Sorry folks there is no valid or a good argument in favour of inhumane treatment of both sides of the family and a best friend of 30 years.
"Snobbery and arrogance are not humanitarian traits. She has an obligation especially to treat our father with kindness."
In an earlier tweet, she compared Meghan to Donald Trump.
She said: "People need to stop being so blinded by glare of celebrity status and wealth.
"Trump said he could shoot someone and not lose votes. The same mentality applies to my sister.
"People believe anything and still follow in an ant line.
"She owes my father a lot of love and respect. No one wants to spoil her marriage and marriage is not at issue.
"What is at issue is the kind treatment of our dad."