A coalition of organisations championing press freedom have rallied behind the award-winning Observer and Guardian journalist Carole Cadwalladr, stating they are “deeply disappointed” she has been refused permission to appeal against a ruling that ordered her to pay significant legal costs to the prominent Brexit backer Arron Banks. The supreme court refused to let Cadwalladr contest a cost order six months ago making the journalist responsible for hundreds of thousands of pounds of Banks’s legal costs. The coalition, which includes Index on Censorship, the Guardian, the Observer and Reporters Without Borders UK among others, warns that the decision risks stifling public interest journalism in the UK. Cadwalladr’s legal team confirmed on Saturday, however, that the fight was not over, revealing that they would be taking the case to Strasbourg. Gavin Millar KC said: “Carole established that over 90% of the publications Banks sued on were lawful public interest speech. So her lawyers believe the order for her to pay 60% of Banks’ costs was a penalty which violated her right to journalistic freedom of expression under article 10 [of the European Convention on Human Rights]. We will seek a ruling to this effect from the European Court of Human Rights.” Millar’s intervention arrived as the UK Anti-Slapp Coalition – campaigning against what it calls “abusive lawsuits filed by a private party with the purpose of silencing critical speech” – issued a statement of support for Cadwalladr. “It is important to reassert that Banks was only successful on less than 10% of the publications he sued on. Yet the application of the UK costs rules for libel means that Carole is now expected to pay a six-figure sum. We cannot have a level playing field when lodging a defence or fighting a case through different courts can threaten your livelihood or render you bankrupt,” the coalition said. The supreme court recently ordered that “permission to appeal be refused because the proposed appeal does not raise an arguable point of law”. It added that the supreme court could not interfere with the court of appeal’s discretion to award costs, unless the court “erred in principle or exercised its discretion in an unreasonable manner, and neither of those conditions is met”. Banks, who donated a record £8m to the pro-Brexit Leave.EU campaign group, sued over comments made by Cadwalladr in a Ted talk and a tweet in 2019. He originally lost his case. Mrs Justice Steyn found Cadwalladr’s remarks were protected when she made them because they were part of reporting on a matter of “real and abiding public interest”, and her belief that publishing those remarks was in the public interest was a reasonable one for her to hold. The judge also ruled that the public interest defence fell away from April 2020, when the Electoral Commission issued a statement confirming it accepted an earlier National Crime Agency conclusion that there was no evidence that Banks had broken the law. But she found Banks had not suffered serious harm as a result of the continuing publication. Steyn added that it was “neither fair nor apt to describe this as a Slapp suit”. Banks then went to the court of appeal, which partially ruled in his favour, concluding serious harm had been caused by the continuing publication of the words complained of in the Ted talk after April 2020. It did not overturn the public interest defence of the original reporting, which the appeal court recognised “absorbed most of the time and money”. The parties later agreed that Cadwalladr should pay £35,000 in damages for the continued publication. However, the costs ruling required Cadwalladr to cover 60% of Banks’s legal bills for the original case, repay some money he had been ordered to pay her in respects of her costs for the original hearing, and pay one-third of his legal costs for the appeal, a sum amounting to hundreds of thousands of pounds. Following that ruling, Banks said: “In my opinion, this case is being driven by Cadwalladr’s lawyers, who banked the win.”