Meghan Markle's half-sister has suggested the royal bride-to-be's humanitarian work could be "exploitative".
Samantha Markle appeared to question why her relative has visited some of the world's most impoverished places in an astonishing TV interview.
Ms Markle has travelled across the world to carry out outreach work including trips to Rwanda to support a clean water campaign and to India to demand better education for girls.
But her estranged half-sibling said she was unsure about the motive of some celebrity figures who visit destitute places "wearing impeccable clothing" and treat it as a "photo opportunity".
In a Mirror interview earlier this month, Samantha revealed she had not talked to Meghan for three years and said she did not know if she would receive an invite to her wedding to Prince Harry at Windsor Castle in May.
Speaking to A Current Affair, an Australian current affairs programme, Samantha said: "I've seen in my lifetime a lot of situations wherein celebrities visit a place that is poverty stricken and they’re wearing impeccable clothing, they themselves are wealthy, and it really feels like just a photo opportunity.
"So that is a little exploitative in my mind."
When discussing their dad, Thomas Markle, Samantha urged Meghan to "step up to the plate" by helping him financially to ensure he is "well taken care of".
The 53-year-old focused on the future royal's dress as an extravagance which proved she could support him.
Samantha told interviewer Lauren Golman: "I don’t think he feels like she owes him, but that is how I see it. If you can afford $75,000 (£53,500) for a dress, you can afford $75,000 to help your dad. That’s how I feel, that’s who I am.
"Honestly what she could spend in a weekend would greatly help dad. so that should be a priority. I think you need to step up to the plate and make sure he is well taken care of."
Retired lighting director Thomas is living a reclusive life in Mexico.
He left the US two years ago after declaring himself bankrupt.
It has not been announced if Thomas will walk Meghan down the aisle at St George’s Chapel at Windsor Castle, Berks.
When asked about giving his daughter away, he told the Mirror: “I’d love to.”
Earlier this month, Samantha spoke movingly of her wish to be reunited with 36-year-old Meghan, who she revealed she has not talked to for three years.
She told the Mirror: “The last time we spoke – when I heard her voice – was 2014, almost 2015.
“Her last words were, ‘I love you, babe. I’m really glad we had this conversation. Keep in touch’.
“And she couldn’t – she got busy. I tried. But I think she just got really busy.”
Breaking down in tears, Samantha added: “I hope now that she knows I was there. I should’ve really reached out more... but I’m proud of her.”
Samantha also denied the title of her forthcoming memoir – The Diary of Princess Pushy’s Sister – is an insult to Meghan, saying she chose it to make a mockery of “social perceptions and labels”.