Hundreds of human rights groups, law professors and activists have urged the British and Swedish governments to abide by a United Nations panel decision that Julian Assange's stay in the Ecuadorian Embassy amounts to "arbitrary detention".
The UN Working Group on Arbitrary Detention said last month that the WikiLeaks founder should be free to leave the embassy in London.
Authorities in Britain and Sweden rejected the finding, saying Assange had detained himself by seeking refuge in the embassy.
Assange has been living in the embassy in central London for more than three years after being granted political asylum by the Ecuador government.
A statement signed by 500 people from more than 60 countries and issued ahead of a meeting of the UN Human Rights Council, condemned the British and Swedish government reactions, saying they were "setting a dangerous precedent that undermines the United Nations Human Rights system as a whole".
"We urge Sweden and the United Kingdom to respect the binding nature of the human rights covenants on which the decision is based, including the International Covenant on Civil and Political Rights, as well as the independence, integrity and authority of the Office of the High Commissioner on Human Rights and the Working Group on Arbitrary Detention.
"We therefore call on the governments of Sweden and the United Kingdom to comply without further delay with the Working Group's findings and ensure the right of free movement of Mr Assange and accord him an enforceable right to compensation."
Among the signatories were Ai Weiwei and Pussy Riot, actor John Cusack, former Greek finance minister Yanis Varoufakis and a number of former UN Special Rapporteurs.
Assange is wanted for questioning in Sweden over a sex allegation, which he denies, but believes that if he goes to Sweden he will be taken to the United States to be quizzed over the activities of WikiLeaks.
