Meghan Markle's estranged sister Samantha Markle has lashed out at Prince Harry, calling his decision not to attend Prince Philip's memorial "petty."

The Duke of Sussex fears for his and his family's safety while in the U.K. without police protection. It is said that he decided against attending the Thanksgiving service for Prince Philip's life on March 29 because of this. But Samantha believes this to be a "childish" excuse especially since it will be a family event where the royal is likely going to get security alongside his relatives.

"I think the bottom line is naturally, he would have security, asking to make security such a big issue seems like some sort of excuse on the grounds that the whole Royal Family are attending," she said in an interview with the Daily Star.

"As the whole world has seen The Duke and Duchess of Cambridge and their children live such high profile lives yet with a resemblance of normality, they don't always take private jets and travel coach (economy). While on royal duty they have security, it's the same with Princess Anne," Samantha cited.

She pointed out the fact that Prince Harry and Meghan Markle are no longer entitled to the benefits that came with being a working royal. This includes their personal security.

"Harry and Meghan stepped down from royal duty and wanted to pursue the red carpets and be American so therefore it only seems right and protocol that they're not entitled to the same benefits that royal duty comes with," she added.

Samantha called it "counter-intuitive and seems childish and selfish" for the Duke of Sussex to ask for police protection, "especially under these conditions and everything that has transpired." She added, "To put something as petty as security ahead of the obvious ethical, humane military and royal respect, it doesn't make sense, it's sad."

Prince Harry, through his representative, announced that he will not be able to attend Prince Philip's memorial on Tuesday. He did not give a reason for his absence but promised to see Queen Elizabeth II soon. He refused to join his family for the poignant ceremony, but he will travel to The Hague in The Netherlands next month to attend the Invictus Games.

Prince Philip Duke of Edinburgh
31 October 2015: Prince Harry, Prince William and the Duke of Edinburgh enjoy the-build up to the 2015 Rugby World Cup Final match between New Zealand and Australia at Twickenham Stadium Phil Walter/Getty Images