Civil rights group Amnesty International launched a campaign against internet censorship on Sunday, accusing multinational companies of complicity in censorship with repressive regimes.

Talking to the Observer newspaper, Amnesty UK director Kate Allen targeted Yahoo, Microsoft and Google for complying with the censorship rules of the Chinese government. She also criticised Cisco Systems and Sun Microsystems for supplying hardware that enables filtering and monitoring of web traffic.

"The internet is big business, but in the search for profits some companies have disregarded their own principles and those on which the internet was founded: free access to information," Allen wrote on the 45th anniversary of the publication of an article leading to Amnesty International's creation.

Technology companies have defended their decision to operate in China, saying they must comply with local laws if they want to do business. Critics have assailed the defence, arguing tech companies have equipped Chinese authorities with advanced tools to repress information.

A report by the OpenNet Initiative study released in April found that China has a "sophisticated" filtering system that encompasses web pages, email messages, blogs, online discussion forums and university bulletin-board systems. The OpenNet Initiative research group is a partnership composed of University of Toronto, Harvard Law School and the University of Cambridge.

Allen wrote that Amnesty has documented internet censorship in Iran, Turkmenistan, Tunisia, Israel, the Maldives and Vietnam.

Amnesty also started a website,, to support the campaign, which will include lobbying governments to release those jailed for activities related to internet use.