Bikini photos of pregnant Kate Middleton to be published in Australian magazine

The controversy over bikini photos of the pregnant Duchess of Cambridge continues with a magazine in Australia planning to also publish them.

Italian gossip magazine, Chi, was the first to run the photos on its front cover on Tuesday, infuriating the royal family who labelled it a "breach of privacy". 

Editor of tabloid Australian magazine Woman's Day, Fiona Connolly, defended its decision to also print the intimate shots, saying they were not taken by a paparazzo, but by a holidaymaker, The Guardian reported.

"She is on a public beach and she was mingling with holidaymakers. There are other holidaymakers in the photos. It’s a very different situation to the nude photos, there is no photographer hiding in the bushes and she is not inside a private villa," Connolly was quoted in Melbourne's Herald Sun.

According to the Daily Mirror, Woman's Day paid about $US150,000 for the set of 39 photographs after winning a bidding war with two other local magazines.

On Chi magazine's front cover, the 33-year-old Duchess is in a blue bikini striding knee-high through the water with the headline "the belly grows", the Daily Mirror reported. 

A second photo shows her husband, Prince William, with his arm around his wife as they walk along a beach on the private island in the Carribean, under the headline "Kate and William honeymoon in three".

It is understood the series of prints also show Kate's sister, Pippa Middleton, on the beach with a man described as her new "boyfriend".

St James's Palace confirmed on Tuesday that paparazzi photos were sold to Chi magazine, the same publication that last year published a 26-page spread of a topless Duchess, the Independent reported. 

Chi is owned by former Italian prime minister Silvio Berlusconi.

The latest photos were taken on the private island of Mustique where Kate was holidaying with Prince William, her sister Pippa and her parents. 

The royal family described it as a “clear breach of privacy”.

"We are disappointed that photographs of the Duke and Duchess on a private holiday look likely to be published overseas," a spokesman added.

It is understood there are also photos of Pippa Middleton on the beach.

A source told Us Weekly that the couple was upset about yet another use of unauthorized photos.

"It's been a real sour note for the end of their trip," the insider says.

"For Catherine, it was the first time she had shown her baby bump, and so for it to be exposed so quickly has shaken her up a little. They thought with the privacy laws on the island they would be able to spend a moment outside of the house without this happening."

In September topless pictures of the Duchess taken at a French chateau were published in a French magazine, Closer, and republished in other magazines, including Chi, The Guardian reported.