Law firm Appleby on Monday sued the BBC and The Guardian, two of the media outlets that reported on Paradise Papers, a huge pile of leaked documents with details on offshore investments by major public figures, in November.

Appleby said the information was confidential and accessing them was a “criminal act”. It has earlier said that its systems were “accessed by an intruder who deployed the tactics of a professional hacker”.

Appleby is also seeking a permanent injunction stopping any further use of the information, and it wants all copies of the documents returned, BBC reported. The law firm said it had overwhelming responsibility towards its clients and colleagues.

In response to the lawsuit, the BBC and The Guardian said they would “vigorously” defend the revelations, which were in the “highest public interest”.

Gerard Ryle, the director of the International Consortium of Investigative Journalists, described the legal challenge as “a potentially dangerous moment for free expression in Britain”.

The information based on the Paradise Papers was released by United States-based International Consortium of Investigative Journalists, through 96 media houses across the world, including The Indian Express. Information from Appleby was the source of about half of the 13.4 million leaked documents.

The records were passed on by an anonymous source to German newspaper Süddeutsche Zeitung, which got together media outlets in other countries to scan the documents to make country-specific findings.

At least 714 Indians were named in documents leaked from Bermuda’s Appleby and Singapore’s Asiaciti, which help the rich and the powerful move their money abroad and invest it in 19 tax havens.