The celebrity magazine 'Closer' said it would publish the topless pictures which were taken when the duke and duchess were on holiday last week at the French chateau of the Queen's nephew in its Friday edition.
The photos are "blurry" and appear to have been taken with a long lens but are clearly of the royal couple, who are now touring Asia, BBC reported.
There are four pages of pictures of William and Kate, with the duchess topless in several of them, and the announcement by the magazine caused dismay in the royal family with BBC quoting Palace officials as saying, "the couple were saddened and disappointed about what they considered to be a breach of their privacy".
They were told about the magazine's plan to publish the photos during breakfast in Kuala Lumpur, Malaysia.
It has emerged that British newspapers were offered photographs last week but turned them down, the report said.
The threat to print photos of topless Kate comes on the heels of the splashing of pictures of a naked Prince Harry, Kate's brother-in-law taken in a Las Vegas hotel room last month.
The royal couple are touring the globe as part of the Queen's Diamond Jubilee celebrations.
They are on a nine-day trip that started in Singapore. After visiting a mosque in Kuala Lumpur today they are expected to move to the Solomon Islands over the weekend and later Tuvalu.
