Pirate Party supporters celebrate their win in the European elections
The Pirate Party - which won a surprise seat in the European Parliament in Sweden - has launched in the UK.
The party, which campaigns to legalise non-commercial internet file-sharing and has branches in 25 countries, plans to contest the next general election.
It gained 7.1% of the vote in Sweden on the back of publicity over the trial of the founders of Pirate Bay, a well-known file-sharing site.
It also campaigns for free speech and against "excessive surveillance".
The party says it wants to reform copyright and patent law and believes peer-to-peer networking should be encouraged rather than "criminalized".
It also wants to introduce an alternative to pharmaceutical patents throughout Europe that it says will save on drug costs to governments.
'No middle ground'
It became an officially registered party in the UK on 30 June and now aims to recruit members and raise funds with a view to contesting seats at the next general election, which must take place before June next year.
UK party treasurer Eric Priezkalns told Sky News: "We think there are a lot of people out there who share our concerns.
"The reason for launching a party is to give those people an opportunity to express their concerns about piracy, about privacy, and about how the mainstream parties aren't responding to that agenda."
He said the Pirate Party was committed to giving creative artists a "fair deal" on copyright and did not want a "free-for-all" - but it did want reform of the existing laws to decriminalize the sharing of material such as music and films.
"With 21st Century technology and the way the laws are now there is no room for sharing. It's either you are buying or you are stealing. There is no middle ground," he added.
The party is also campaigning against proposals contained in the recent Digital Britain report to crackdown on illegal file-sharing.
The plans, which could form future government policy, include sending warning letters to those making illegal downloads and allowing internet service providers to release the identities of serial infringers to make it easier for music and film companies to sue them.
The entertainment industry claims it is losing tens of millions of pounds in the UK alone every year to internet piracy.
The profile of the Pirate Party in Sweden was boosted in the run-up to May's European elections by the trial of the four men behind Pirate Bay, who were sentenced to a year in jail and ordered to pay $4.5m (£3m) in damages.