The UK is among a host of European Union (EU) nations to have signed up to the controversial Anti-Counterfeiting Trade Agreement (ACTA) amid concerns the legislation will lead to censorship of the web.
A statement from Japan's Ministry of Foreign Affairs said that as of 26 January, 22 European member states will adhere to the agreement.
The signed-up nations include France, Spain, Ireland and Italy. Other EU members are expected to enter the agreement after completing what the ministry termed "domestic procedures".
The signing adds the EU to a group of ACTA members which already includes the US, Canada, Japan and Australia.
The agreement was first ratified and signed in October of last year and is designed to place international guidelines on copyright enforcement online.
The EU's signing has drawn a fresh round of protests from online campaigners, who argue that ACTA will place excessive constraints on file-sharing and violate consumer rights.
Among those who have protested against the signing is hacktivist group Anonymous.
Using the movement's trademark "Expect Us" warning, groups connected with Anonymous have promised to take action against the EU, leading to some speculation that a large-scale attack was looming.
Thus far, however, the group has remained mostly peaceful in its efforts. Twitter accounts affiliated with Anonymous have been directing users to an online petition opposing ACTA.
Online activist groups took similar actions earlier this month when the US congress was considering a vote on the Stop Online Piracy and Protect Intellectual Property Acts (SOPA and PIPA.)
Following protests which included a self-imposed blackout on many prominent sites, the Senate decided to table the bills indefinitely.
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