The Duchess of Sussex's estranged half-sister has claimed she will hold her ''responsible'' if their father dies after she allegedly ''froze him out'' after the wedding.

The 36-year-old former actress' relative Samantha Markle has launched yet another scathing attack on her and her new husband Prince Harry, whom she married two months ago, and has branded her ''cold'' for ignoring her dad Thomas Markle.

Taking to her Twitter account after she saw pictures of the royal couple visiting a London exhibition on Nelson Mandela, Samantha tweeted: ''Glad you have so much time to gallivant around paying tribute to others while ignoring your own father!

''How can you be so cold and look in the mirror? Harry? I guess I was right. Act like a humanitarian act like a woman! If our father dies I'm holding you responsible, Meg.''

Her cruel words come just days after Meghan's father said he was heartbroken that he hadn't spoken to his daughter since before she joined the royal family in May.

He said: ''If I chose in a month, or couple of months, to go to En­g­land - I want to see my daughter. I'm thinking about it. I don't care whether she is p***** off at me or not. I'm not going to wave flags and make a fool of my­self. I'd find a hotel room and try to reach them ... My thing about my daughter right now is that I think she is terrified. I see it in her eyes, I see it in her face and I see it in her smile. I've seen her smile for years. I know her smile. I don't like the one I'm seeing now. This one isn't even a stage smile - this is a pained smile. That might be just having a couple of bad days. I don't know. It really worries me. I think she's under too much pressure.''

Thomas came under fire just a few weeks before the royal wedding after he staged paparazzi photos that saw him getting measured for a suit for the big day.

A few days later, Kensington Palace released a statement stating that Thomas would not be walking Meghan down the aisle as he had to undergo heart surgery in the US.

The retired lighting director explained: ''It's sad that it's got to this point.

''I'm sorry it's come to this. Yes, some of it is my fault. But I've already made it clear that I'm paying for this for the rest of my life.''