The service offers anonymous use of the internet

Relakks, as the service is known, allows users to send and receive files through a heavily-encrypted connection.

It claims to be the first commercial darknet, a virtual network set up to share files between trusted users.

The service is endorsed by political group the Pirate Party which is running for election in Sweden under a banner to reform the country's copyright laws.

"There are many legitimate reasons to want to be completely anonymous on the internet," said Rickard Falkvinge, chairman of the Pirate Party.

"The right to exchange information in private is fundamental to the democratic society. Without a safe and convenient way of accessing the internet anonymously, this right is rendered null and void."

Closed groups

A darknet is a cordoned-off, anonymised section of the net where users can meet, chat and swap data.

Usually darknets are confined to small tight-knit groups such as hackers who use the secure connections to distribute information and hacking tools.

We don't have any control over what is being sent over the network but that's the point Rickard Falkvinge

They have also been used by paedophiles to distribute images of child abuse.

Many are invitation-only services where potential members have to upload material to prove themselves to the group before they are granted full access.

Similar identity-hiding tools such as Tor are used by net dissidents in countries like China to avoid persecution for their activities on the web.

Some previous attempts to launch large scale anonymous networks, such as Nullsoft's Waste program have been unsuccessful. After its release in 2003, Waste was removed from distribution by Nullsoft's parent company AOL.

Unique service

The new system claims to be the world's first commercial darknet. It is provided by Swedish company Relakks and is endorsed by the Pirate Party.

It works by giving a user's computer a new IP address, the unique number the machine uses to identify itself and communicate with other machines over the net.

Copyright law and file-sharing are divisive topics in Sweden

IP numbers allocated by your internet service provider (ISP) can be used to trace and identify a specific computer on a network.

Computers using the Relakks system look like they have a Swedish IP address, no matter where they are in the world.

Users can then share files, such as music or films, with any other users. In theory anyone monitoring user's online activities will not be able to trace their geographical location.

The Pirate Party acknowledge that the service could be used to distribute copyright material or other content such as images of child abuse.

"We hear the argument a lot," Mr Falkvinge told the BBC News website. "No, we don't have any control over what is being sent over the network but that's the point.

"People who want to hide their activities online already have the means to do so. We're just giving those tools to the general public."

Democratic rights

File sharing and copyright law is a divisive topic in Sweden. Until recently the country was a hotbed of piracy where films, music and software were readily swapped online.

Last year, it outlawed the unauthorised downloading of copyrighted movies and music in an attempt to curb piracy, after criticism from Hollywood.

What is the difference between trusting them and trusting my own ISP not to give me away? Smirnov

The Pirate Party was launched in part to temper what they say are "aggressive" tactics by the entertainment industry to enforce copyright infringement.

They say techniques such as tracing IP addresses threaten privacy and democracy.

The Relakks service, they say, offers people the ability to use the internet "without fear of being monitored or logged". It costs five euro (�3) per month with some of the funds going towards supporting the Pirate Party.

However, not everyone is convinced that it is what it claims to be.

Many dispute whether Relakks really is the first commercial darknet. Other services like Hamachi and Groove already offer similar services.

In a forum on the website of the US Pirate Party, an affiliated but distinct political group, a post by a user called Smirnov also questioned whether the service is really anonymous.

"You can't connect to Relakks anonymously, because then they'd have no way of verifying you are a paying customer - so Relakks knows who you really are when all your traffic goes through them.

"What is the difference between trusting them and trusting my own ISP not to give me away?"