Did the Swedish king visit strip clubs, and why did his friend seek a gangster's help to snuff out the scandal?

Those questions have the nation in a tizzy and are posing the monarchy its most serious challenge during Carl XVI Gustaf's nearly four decades on the throne.

The media, much less enthralled by the royal family than the public, is attacking the 65-year-old monarch with unprecedented fury, although on Monday, he denied the allegations in an interview with Swedish news agency TT.

One leading newspaper has urged the king to step down, while others suggest he should go if it turns out he was lying when he denied visiting strip clubs in the U.S. and Slovakia, claims first presented in a book published last year.

"His reputation has of course been hurt by this and he's had a difficult time defending himself," said royal commentator and writer Roger Lundgren. "But this has certainly taken on proportions that are approaching the grotesque."

At the heart of the scandal is The Reluctant Monarch, a book released in November that for the first time put into print long-standing rumours about the private life of Carl Gustaf, who has three adult children with his German-born wife, Queen Silvia.

The book alleged that the king had a secret love affair in the 1990s and described how he and his friends frequented private night clubs in Stockholm where they were entertained by scantily clad women. It also claimed he visited exclusive strip clubs during foreign visits — in Atlanta during the 1996 Olympics and in Slovakia in 2008 — citing former employees of those establishments.

Book slammed as gossip magazine

Many of the allegations are poorly sourced and critics say the book, which was presented as a biography, amounts to nothing more than a gossip magazine in hardcover.

The king's supporters say he's the victim of a malicious slander campaign fuelled by republican forces who normally don't get much attention in Sweden.

Most Swedes want to preserve the constitutional monarchy even though it's widely seen as contradicting the principles of democracy and equality that underpin Swedish society. The monarchy's survival hinges to a large degree on its popularity.

"The Swedish royal court, like the Danish and Norwegian, depends on widespread trust from the public," political editor Peter Wolodarski wrote in the Stockholm daily, Dagens Nyheter. "The day people start to doubt whether the top representatives of the royal court are telling the truth, they [the royals] live dangerously."

'If it turns out that the king lied straight into [Swedes'] faces, we could be one step closer to a republic.'—Goteborgs-Posten, Swedish newspaper

A recent poll showed about 44 per cent of the Swedes wanted Carl Gustaf to remain king, while 17 per cent said he ought to give way to his eldest daughter, the popular 33-year-old Crown Princess Victoria.

Research institute TNS-Sifo interviewed 1,000 people for the May 25-26 poll. The margin of error was two to three percentage points.

A similar poll around 12 months ago, showed 64 per cent of Swedes wanted the king to stay on the throne.

Carl Gustaf first addressed the allegations in a somewhat confused monologue to reporters at his annual moose hunt in November, saying his family was "turning the page." He didn't deny the allegations, which was seen by many as a partial admission.

It might have been expected to end there. After all, the king was not accused of anything illegal and Swedes don't get into a moral panic about extramarital affairs. But the question of strip club visits, frowned upon in Sweden's egalitarian society, would not go away.

And suggestions the king may have spent hefty sums on such visits raised questions about whether the public should be provided more information about how the royal court uses its annual nearly $20 million US taxpayer-funded stipend.

King's friend admits to contacting criminals

In May, the story took a new twist when Swedish Radio aired a secret recording in which one of the king's friends, Anders Lettstrom, was heard discussing the scandal with a reputed gangland figure. Their conversation centred on Mille Markovic, a former night club owner and a key source in the book who claims to have pictures of the king's entourage in compromising situations.

Swedish Radio broadcast parts of a conversation where Lettstrom wanted to know exactly what material Markovic had and how much it would cost to make him hand it over.

After initial denials, Lettstrom issued a statement to TT admitting he had contacted criminals in a misguided attempt to find out "how so many lies about me and others" could have been spread in the book about the king. Lettstrom said he had acted alone and that the king knew nothing about it.

Under mounting media pressure, the king agreed to an interview with TT about his private life on Monday. He rejected any knowledge of Lettstrom's contacts with criminals and said he no longer considered Lettstrom a friend. He also denied having visited the specific strip clubs mentioned in the book.

In answer to whether he had ever visited a strip club, the king asked the reporter to define what exactly he meant by one, then recalled a visit to a cabaret in Paris.