Meghan, Duchess of Sussex, is being “vilified and chased” by the tabloid press in the same way the late Princess Diana was, Hollywood superstar George Clooney has told an Australian magazine.

Clooney, a close friend of the duchess formerly known as actress Meghan Markle and her husband, Prince Harry, warned of “history repeating” itself with the increasingly feverish media attention on the expectant royal couple.

“I do want to say, they’re just chasing Meghan Markle everywhere,” Clooney told Who magazine during an interview in Los Angeles. “She’s a woman who is seven months pregnant and she has been pursued and vilified and chased in the same way that Diana was, and it’s history repeating itself,” he added. “We’ve seen how that ends.”

Diana, Princess of Wales – Prince Harry’s mother – died following a car crash in a Paris road tunnel in 1997 while being chased by paparazzi on motorcycles.

Amal and George Clooney arrive at St George’s Chapel, Windsor Castle, for the wedding of Meghan Markle and Prince Harry in May 2018. Photograph: Reuters

Britain’s famously aggressive press at first welcomed Markle into the royal fold when she and Harry tied the knot at a lavish Windsor Castle wedding last May, in a ceremony attended by Clooney and his wife Amal, a human-rights lawyer. The actress was credited with breathing fresh life into a monarchy sometimes labelled stale and out of touch.

But coverage has turned increasingly critical – despite the impending birth of the couple’s first child – with reports of palace sniping over her manner.

Tabloid newspapers have also luxuriated in stories about the duchess’s fractured American family. Last week, one paper published a highly personal letter they said was written by the duchess to her estranged father in which she begged him to “stop lying … stop exploiting my relationship with my husband”.

Clooney, who was promoting his new TV series, Catch-22, slammed the invasion of her privacy. “I can’t tell you how frustrating that is, just seeing them broadcast a letter from a daughter to a father, she’s getting a raw deal there and I think it’s irresponsible and I’m surprised by that,” he said.

The Duke of Sussex and his older brother, Prince William, Duke of Cambridge, have had a difficult relationship with the media since the death of their mother. Prince Harry recently revealed that for a long time he struggled to cope with her death, and sought professional help a few years ago.