An advertisement that used Princess Diana’s admission of adultery to promote condom sales stirred protests from Britain and furious debate in Norway.

The newspaper ad showed a photograph of the British princess, wearing white, on one page. On the opposite page was the headline: “It’s hard to see on the outside whether someone has had casual sex with casual partners.

“It happens in the best of families. One can never be too careful,” said the ad for RSU condoms, published by the Oslo tabloid Dagbladat on Friday.

The ad appeared the day after Norwegian television aired a British Broadcasting Corp. interview in which the princess admitted to having been unfaithful to her husband, Prince Charles.

Norwegian newspapers reported Saturday that Buckingham Palace was furious about the advertisement, which used Diana’s picture without permission.

“The palace has asked the British Embassy in Norway to consider possible reactions,” the Oslo newspaper Verdens Gang quoted palace press officer Charles Anson as saying.

The ad also got a sharp response in Norway. Former Prime Minister Jan D. Syse called it “evil-minded.”

But the man behind the campaign, Ingebright SteenJensen of the JBR agency in Oslo, said the ad was motivated by the need to promote the use of condoms to prevent the spread of sexually transmitted disease.

“As we see it, it was Diana who made her life above and below the belt the No. 1 topic of conversation this week,” he said. “She must have known that her statements would be used commercially around the world.”