More than a dozen senior journalists, media workers and rights campaigners have published an open letter demanding the British government do more to protect the press from so-called strategic litigation against public participation (SLAPP) lawsuits.
"Such legal threats are designed to inhibit ongoing investigations, and prevent legitimate public interest reporting," said the letter, which was signed by Paul Webster, editor of London-based Sunday newspaper The Observer and PEN International chief Carl MacDougall.
"This isn't about an attack on me, it's an assault on journalism," said Cadwalladr in a tweet. "We cannot let millionaires use the courts to bully and harass and suppress critical reporting."
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'Threat to media freedom'
Earlier this month, lawyers representing Brexit financier and Leave.EU co-founder Arron Banks filed a legal claim against Cadwalladr in what the letter described as "another example of a wealthy individual appearing to abuse the law in an attempt to silence a journalist."
"The increasing deployment of what appear to be SLAPP lawsuits in the UK poses a threat to media freedom and public interest advocacy, and demands a robust response," the letter said. "We believe that new legislation should be considered to prevent the abuse of defamation law to silence public interest investigative reporting."
Banks has reportedly filed a lawsuit against Netflix ahead of the release of its documentary film The Great Hack, about "how a data company named Cambridge Analytica came to symbolize the dark side of social media in the wake of the 2016 presidential election."