Image caption Sweden's Princess Victoria and Prince Daniel personify the country's reputation for wealth, beauty and equality

Anti-corruption watchdog Transparency International has consistently ranked Sweden as one of the best countries in the world in which to do business.

It's a perception Swedes share. And they're very much attached to it.

Walking down the sparkling clean streets of the capital, Stockholm, I stopped Swedes on the street to ask them. "Yes," they said, "there is a Swedish way of doing things: discuss, agree, do good."

"We see ourselves as a model for other countries," one woman told me.

At the anti-corruption unit in central Stockholm, chief prosecutor, Gunnar Stetler said the phone rang frequently.

Extreme World is a new season of coverage on TV, Radio and Online, examining global differences. Over the next few months, BBC News correspondents will be exploring eight key themes that illustrate the divisions in our extreme world. Special Report: Extreme World World 'is becoming more corrupt'

Mostly, he said, it was people saying that their neighbours had built a wall or painted the house green and complaining that planning permission must have been obtained by corrupt means.

Hardly the stuff of crime novels.

"It's not that we are better than you," said Mr Stetler, "but we are more transparent, and that makes it harder to be corrupt."

He then offered to show me his record of expenses, because in Sweden anyone has the right to check a public official's expense claims.

But our trip for the Extreme World series, looking at the extreme lack of corruption in Sweden, coincided with a national debate over whether this image is really true.

The news headlines were dominated by a scandal in Gothenburg. Police were investigating allegations that local government officials had accepted bribes from a major construction company.

Swedes were shocked at the possibility, and editorials in the popular papers were asking whether Sweden was as clean as it thought it was.

'Dark corners'

Henning Mankell, the writer behind the hit Swedish detective series Wallander, says Sweden is a "very decent country" but he believes there has long been a myth that it is perfect.

He says that in his books, which examine the uneasy aspects of Swedish society, he aims to be part of "Sweden's conscience".

If people don't think they'll be investigated, they'll probably take the chance to be a little bit corrupt Gunnar Stetler, Stockholm anti-corruption unit

"What I try to do is maybe give a more realistic view of Sweden… Sometimes it's needed to take a torch and look into the dark corners."

Mr Mankell says Swedes feel betrayed by the scandal in Gothenburg, and are asking whether this transparency made them complacent. Do they recognise corruption when they see it?

On a bright summer's day, Princess Victoria married her personal fitness trainer at her local church, in central Stockholm. A huge crowd turned out to cheer.

The royal couple personify Sweden's reputation for wealth, beauty and equality.

But the honeymoon was less popular. A Swedish business tycoon flew the royal couple on a private jet to a luxury yacht.

Potential risk?

Peter Wolodarski, political editor of Sweden's daily Dagens Nyheter newspaper, says public figures should not be indebted to private business.

He believes that it might be helpful for the billionaire, who owns the world's largest language training firm, to have the royal family open doors.

Five Least Corrupt countries Denmark

New Zealand

Singapore

Finland

Sweden Source: Transparency International corruption perceptions index 2010

"There is a potential risk," says Mr Wolodarski, "that the royal family repays a favour to a man like that."

The royal family said the trip was private, and a wedding gift from a family friend.

Mr Stetler looked into opening an investigation into the honeymoon gift, but decided the Swedish constitution put the royal family beyond the country's anti-corruption laws.

The unit did launch an investigation into another national icon though - Saab.

The company does not just make cars, it makes Gripen fighter jets, precision military hardware, and a source of national pride.

Five Most Corrupt countries Somalia

Burma

Afghanistan

Iraq

Uzbekistan Source: Transparency International corruption perceptions index 2010

A television advert calls the Gripens "the wings of a nation".

The anti-corruption unit investigated allegations that Saab used a middleman to bribe the South African government to secure a lucrative order.

Saab refused an interview but said in a statement that it did not consider that it had committed any illegal acts.

"For us at Saab, it is extremely important that we conduct our business with high ethical standards and we act with zero tolerance for bribery.

"The preliminary investigation was conducted over several years, and Saab assisted at all times by openly sharing the information requested."

The prosecutor dropped the case for lack of evidence.

'A bit naive'

But Nils Resare, who has written a book on the Gripen affair, says "it doesn't really matter if you ask Saab about it. You have to have an independent prosecutor do a serious investigation. After that, then we can tell if they are guilty or not."

In his opinion, the prosecutor dropped the case because he couldn't get enough staff to work on finding evidence. "And this," says Mr Resare, "is probably the biggest corruption scandal in the history of Sweden."

The Organisation for Economic Co-operation and Development also criticised Sweden for not putting enough staff on the case.

Mr Stetler took up his post after the case was dropped. But he says that his unit could still use more staff. He has to rely on other departments lending him police officers.

He says the general lack of corruption in Sweden has made his fellow countrymen "bit naive".

"If you're not aware, you don't allocate resources and you don't understand the importance of fighting corruption.

"And if people don't think they'll be investigated, they'll probably take the chance to be a little bit corrupt," he warns.

Mr Mankell says he does not believe Sweden is becoming more corrupt, but he thinks Swedes have woken up to what corruption there is in Sweden.

"Now we have the possibility to stop it," he says.

And although Sweden is not as squeaky clean as we, or Swedes, thought, people here do seem committed to doing something about it.

We were invited to Stockholm's business district to attend a corporate workshop on how to avoid bribery.

There were leaflets on what could constitute a bribe. Businessmen and women took notes in the auditorium.

Main speaker Helen Waxberg told us it was not a big problem in Swedish business. Why hold the workshop then? It's about prevention, not cure, she said.

"We want Swedish business to be best in class."

Listen to Pascale Harter's radio documentaries on corruption in Sweden and Somalia - countries which routinely occupy opposite ends of corruption league tables.