A group of six journalists are taking legal action against London's Metropolitan Police and the Home Office after it was revealed that they had been been under government surveillance for years — and had even been listed as 'domestic extremists'.

Surveillance records, obtained via public records request, detailed the extent to which they police had been spying — reams of documents, including family members' medical history, that led one of the claimants to compare the Met Police to "the Stasi".

They were all targets of the Yard’s National Domestic Extremism and Disorder Intelligence Unit (NDEDIU).

According to a statement from the National Union of Journalists, the political policing this case demonstrates "threatens press freedom."

The organisation, which has hired Bhatt Murphy Solicitors to take the case, said that the lawsuit is just the latest step in a years-long running campaign against the chilling effect — government suppression of free speech.

"This is another extremely worrying example of the police monitoring journalists who are undertaking their proper duties," UK journalism professor Paul Lashmar told the AP.

One of the spied-upon, 21-year-old Times journalist Jules Mattson said: "While some of what I've seen in my files is almost amusing up to a point, it's also sinister and upsetting.

"It appears that records of every time I've been a victim of crime have been transferred to the domestic extremism unit with details of my phone number and past addresses, appearance, childhood and even a family member's medical history recorded."

Another, 44-year-old freelancer Jason Parkinson said he received 12 pages of 140 surveillance logs spanning nearly a decade: "The files make it very clear they have been monitoring my movements, with whom I associate and even what clothing I wear, in order for police intelligence units to build up a profile of me and my network of associates and contacts.

Both he and freelance photographer David Hoffman likened the Met to "the Stasi".

Mark Thomas said the 'domestic extremist' database on which he and his peers feature "seems to be part of a disturbing police spying network, from the Stephen Lawrence family campaign to Hillsborough families, from undercover officers' relationships with women to the role of the police in the construction blacklist."