The photos of the 31-year-old Kate surfaced featuring her in a blue bikini that showed a barely rounded lower belly.
Middleton and her husband were on vacation on the exclusive Caribbean island of Mustique in St. Vincent and the Grenadines when they were spotted.
Italian magazine Chi published the images of the pregnant Duchess of Cambridge on Wednesday, inciting protest and disapproval from the palace.
“We are disappointed that photographs of the duke and duchess on a private holiday look likely to be published overseas. This is a clear breach of the couple’s right to privacy,” a spokeswoman from St. James Palace said in an official statement on Tuesday.
Chi belongs to Mondadori publishing house whose owner is former Italian Prime Minister Silvio Berlusconi. The same magazine published photos of Princess Diana’s dying in a tunnel in Paris after a high-speed car chase with paparazzi in 1997.
“Everybody is entitled to privacy, but it’s just different when you’re a royal,” said Victoria Arbiter, royal contributor for ABC News. “They all crave normality, but they’re not just like everybody else.”
Alfonso Signorini, the editor of Chi, denied the palace’s allegations that the images were an invasion of privacy.
“The photographs can hardly be considered an invasion of privacy when the subjects are public figures in a public place,” he told reporters. “What out readers will see is simply a moment of joyful relaxation being enjoyed by a smiling, happy couple. Where’s the scandal in that?”
He also explained why he decided to publish the photos of the pregnant Duchess of Cambridge.
“The article features photos of a young couple in love as they happily walk along the shore,” he said. “They are images of such unexceptional normality that there is only limited mention of them on the cover of the magazine.”
“Moreover, the photographs can hardly be considered an invasion of privacy when the subjects are public figures in a public place, in the open air; specifically on a beach surrounded by other bathers,” Mr Signorini added.
Women’s Day editor Fiona Connolly also defended the photographs, claiming no boundaries had been crossed. “There is no photographer hiding in the bushes and she is not inside a private villa,” she said.
In the five-page photo spread in Star, the royal couple looks absolutely fallen in love as they stroll on the beach together with William’s arm lovingly around his wife. They are seen frolicking in the waves, and look more in love than ever, reports The Hollywood Life.
“William joined Kate for an early morning swim; they were touching and kissing in the waves. When they came out of the water, he got down on his knees in front of Kate and kissed her baby bump,” an onlooker told Star magazine.
“He then hugged her and held her as they watched the sunrise together. You could tell it was a magical moment for them,” the source added.