Human rights group Liberty is taking judicial review proceedings against the law, also known as the Snoopers’ Charter, on the basis that it provides for unlawful “bulk surveillance”.

The law provides the security services with powers, under warrants issued by judicial commissioners, to hack computers and phones and intercept people’s communications.

Documents disclosed during the course of the judicial review have revealed that MI5 has failed to meet its legal duties under the IPA for as long as it has been law.

The NUJ maintains there is inadequate protection for journalists, their equipment, materials and sources.

The union will argue before the High Court on Monday that the bulk surveillance powers in the Act permit an interference with journalistic communication, that the safeguards to protect journalistic sources are inadequate, and that the powers in the Act threaten to undermine the vital public watchdog role of the media.

It argues that other legislation, such as the Police & Criminal Evidence Act 1984 and the Terrorism Act 2000, provides safeguards and requires an opportunity to be heard prior to journalistic material being seized.

Roy Mincoff, NUJ legal & industrial officer, said: “The Act falls far short of the protections, even if limited, in other legislation. That the Government has now had to admit that MI5 has already broken the law both as to the obtaining and retention of information shows just how vigilant we must be to prevent this happening again.

“It emphasises the need for the IPA to be amended to significantly strengthen safeguards for journalists and their sources.”

Michelle Stanistreet, NUJ general secretary, added: “These breaches by MI5 and its failure to provide information to senior judges should give everybody a great cause for concern. The security services must never be beyond the law.”