The block on payments to the whistleblowing Web site followed its publication of sensitive US diplomatic cables and has so far choked off more than 95% of donations, costing the organisation in excess of $20 million.

WikiLeaks filed a formal complaint with the European Commission in October 2011, claiming that Visa and MasterCard are in breach of EU anti-trust laws.

The EU executive body has yet to formally rule on the complaint, but in a statement to Reuters, a Commission spokesman says: "On the basis of the information available, the Commission considers that the complaint does not merit further investigation because it is unlikely that any infringement of EU competition rules could be established."

WikiLekas' head Julain Assange has vowed to fight on: "It is concerning that hard-right elements in the United States have been able to pressure Visa and MasterCard, who together hold monopoly over the European market, into introducing a blockade that the US Treasury has rightly rejected. These unaccountable elements are directly interfering in the political and economic freedoms of EU consumers and are setting a precedent for political censorship of the world's media."