Finland's prime minister, who accused his former lover of hurting his feelings by writing a steamy kiss-and-tell account of their relationship, lost a court case over the book last week but unexpectedly gained popularity.

Matti Vanhanen, 52, prime minister since 2003, has been enjoying a wave of support since the disclosure that he likes to take a sauna before sex and enjoys his favourite meal of beef and baked potatoes afterwards.

In her memoir The Prime Minister’s Bride, the spurned lover Susan Ruusunen, 36, wrote: “Once, when he kissed me, he said that I tasted better than oven-baked potato.”

A poll for Finnish television showed that 72% of voters believed that Vanhanen’s credibility was intact and only 19% thought he had lost ground because of the revelations.

Ruusunen timed the publication of her book for just before last year’s general election, which was expected to be a tight race between Vanhanen’s Centre party and the Social Democrats.

When she became a media darling, political pundits predicted electoral disaster but the voters thought otherwise. The prime minister was transformed from a colourless politician into a national sex symbol. He was reelected.

Minutes before the polls closed, it emerged that he had complained to the police about the book. Ruusunen and her publisher faced charges of violating his privacy.

The trial appears to have provoked a backlash against Ruusunen and she was forced to make a public display of contrition. “I’m ashamed of the book and I want to apologise to Matti, whom I’ve hurt,” she said.

The Helsinki court acquitted Ruusunen and her publisher, although the jury was split.

The real winner appears to have been Vanhanen, jokingly dubbed Finland’s sexiest man by Jacques Chirac, the former French president. Vanhanen’s public standing has never been higher. Other scandal-hit politicians will be jealous.

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