Major record companies in Britain have launched their second offensive against the Pirate Bay, demanding that a U.K. political party stop running a workaround to let the country's internet users access the file-sharing site.

A number of British internet service providers, or ISPs, were ordered by the country's High Court earlier this year to block access to the Pirate Bay. That prevented millions of internet users from directly accessing the website at The PirateBay.se.

A screen grab of the main page on the Pirate Bay website. Users enter the name of a movie, song or TV show they want to download into the search window, and the results return a list of links to other sites that will initiate the file-sharing process. (CBC)

But the Pirate Party UK — a political entity that's independent from the Swedish-based Pirate Bay or the Swedish Pirate Party — set up a workaround known as a proxy server to allow access.

On Thursday, the British Phonographic Industry, which represents the major recording labels in the U.K. as well as hundreds of smaller record companies, sent the British Pirate Party a letter demanding that the proxy service be shut down, various media reported.

According to the BBC, the letter said, "Freedom of expression is not an absolute right. It comes with a duty to respect the rights of others, including those whose talent, hard work and investment help to create music and other entertainment."

Pirate Party UK Leader Loz Kaye told the file-sharing news site Torrentfreak that his organization set up the proxy server to combat internet censorship.

"The battle against censorship and indeed the use of site blocking to deal with issues like copyright infringement is disproportionate and not productive. Issues like these are at the core of why we exist and why we want to change the current system and stand up for internet users," he said.

Kaye said the Pirate Party UK would respond to the recording industry association by the end of next week.

The Pirate Bay website has been a focal point for the debate over freedom on the internet vs. copyright protection for creative works. The site does not itself distribute any copyrighted content, but it provides a database of "torrents" that allows users to swap files on the BitTorrent network.

The website's infrastructure was raided by Swedish police in 2006 and four of its operators charged with promoting copyright infringement in 2008. The were found guilty in 2009, lost two appeals within Sweden and are now appealing to the European Court of Human Rights.

Access to the Pirate Bay has not been blocked in Canada. In September, web advertisements promoting the federal government's stimulus spending accidentally appeared on the Pirate Bay site due to a glitch that the Finance Department traced to Yahoo, and which Yahoo in turn blamed on ISP Sympatico. The ads were quickly pulled.