Meghan Markle and Prince Harry fail to publicly acknowledge senior royal on their birthday

Princess Kate and Prince William tweeted: "A very happy birthday to Her Majesty The Queen!"

However, the Duke and Duchess of Sussex did not publicly send their regards to Camila.

Prince Harry reportedly has a strained relationship with his stepmother.

In May, royal commentator Tom Bower blasted Prince Harry's behaviour towards his stepmother as "appalling" during an interview with GB News.

Bower also labelled the multiple digs the Duke of Sussex fired at Camilla in his autobiography Spare as "very unnecessary".

"He's said some terrible things and it was unnecessary.

"And I can believe that she lost her temper with him, lost her cool with him.

"The sort of thing that Camilla would have said is quite frankly that he has behaved atrociously.

"And that is of course before she read or heard what he said about her in the book, which was really very unnecessary."

In April, Camilla's son hit back at claims made by Prince Harry about the Queen.

Tom Parker Bowles is the eldest child of Camilla and Andrew Parker Bowles, who were married from 1973 to 1995.

He told The News Agents podcast: "I think change happens but I don’t care what anyone says – this wasn’t any sort of end game."

Parker Bowles added: "She married the person she loved and this is what happened."

The Duke of Sussex wrote in his memoir that he felt Camilla played the “long game” for marriage to his father and the crown.

He said regarding Camilla: "I have complex feelings about gaining a step-parent who I thought had recently sacrificed me on her personal PR altar."

Harry also claimed Prince William "begged" King Charles not to marry Camilla over fears she would become their "wicked stepmother".