The lawyers representing the reporters from UK-based Doughty Street Chambers and Howard Kennedy said 45 journalists and 315 family members had been targeted in the past six weeks in what they described as a campaign of intimidation.
The journalists were told they would be killed unless they resigned by specific deadlines, all of which have now passed, the lawyers said.
Iran International, which reports on events in Iran and the wider region, said its staff had faced sustained harassment since the channel was founded in 2017, including threats of assassination and kidnapping, physical assaults, online abuse, and hacking.
British lawmakers have warned that Iran is among several foreign governments engaged in transnational repression on UK soil.
A July report from parliament’s Joint Committee on Human Rights said Tehran’s tactics include “assassination plots, physical attacks, intimidation of family members, asset freezing, judicial proceedings, smear campaigns, online abuse, surveillance and digital attacks such as hacking, doxing and impersonation."
Iran International filed an urgent appeal with United Nations experts last week, urging them to take action against Tehran over serious risks to the lives and safety of their journalists worldwide and relatives inside Iran.
On Thursday, US-based advocacy group United Against Nuclear Iran (UANI) called on Washington and its European allies to confront Iran’s transnational repression by issuing a credible military threat, a week after they accused Tehran of plotting to kill individuals in Europe and the US.
Since its formation in 2017, Iran International journalists have been targeted by the Iranian authorities for their reporting. However, since the start of a 12-day war between Iran and Israel in mid-June, the situation has deteriorated rapidly and there is now a real risk to the lives of multiple Iran International staff and to their family members.