Sweden's tax authorities are seeking the bare facts about webcam strippers' income, estimating that hundreds of Swedish women are dodging the law.

The search involves tax officials examining websites that feature Swedish strippers, in an effort to identify them and chase them for tax returns.

The tax loss is estimated at about 40m Swedish kronor (£3.3m) annually.

Project leader Dag Hardyson said 200 Swedish strippers had been investigated so far. He said the total could be 500.

"They are young girls, we can see from the photos. We think that perhaps they are not well informed about the rules," said Mr Hardyson, head of the tax authority's national project on internet trade.

The investigation into strippers is part of a wider tax project that includes online poker and fake trader locations.

Detective work

Mr Hardyson told BBC News that the strippers could be liable to pay about half of their earnings in tax. Striptease via webcam is quite legal in Sweden, unlike prostitution, he added.

"I don't think they have any costs really - almost 100% of what they earn is pocketed. Many have regular work and this is extra income. We want them to register their activity as a business - it's still taxable, even if it's a hobby," he said.

He stressed the difficulty of identifying strippers, saying the contact information on the websites was often "not obvious".

"We have to visit the companies behind the websites to get the information, then we have to work with the electronic wallets where the money is going in."

He said the Swedish tax authorities had been tipped off about Swedish internet strippers by the Dutch authorities, who had started a similar investigation earlier.

Web search tools like spiders had failed to detect the Swedish strippers.

"When we investigated the sites manually it worked better," he added.