DISSIDENT republican group Saoradh is pursuing legal action against Facebook.
The group, which was founded in 2016, has accused the social media giant of political discrimination amid claims it removed pages from its platform.
The party also claims security service MI5 and the PSNI have exerted pressure on the company to remove the pages.
Facebook said it cannot comment "as this is a legal matter" but confirmed it had received a letter of complaint from lawyers acting for the party.
According to BBC NI, a Belfast law firm representing the party - which campaigns for the release of all republican prisoners - is seeking a court order bid to force the company to re-instate a number of pages.
A letter to the company claims the decision to remove the pages was taken "due to our client's particular political view".
It is claimed this is a breach of the right to freedom of expression as set out in Article 10 of the European Convention on Human Rights.
Solicitor Darragh Mackin said: "Facebook has now taken to remove what they deem to be unacceptable political messages, that sets a very, very dangerous precedent and it's an attack, a deliberate attack, on the freedom of expression.
"Therefore our clients have no alternative but to seek injunctive relief to compel Facebook to uphold what is a very, very basic principle, the right to a political opinion and the right to expression."
Mr Mackin said his client had "grave concerns that there are third parties at play".
"Given the fact that the police and security service are known to monitor and intercept communications, I think it's implausible to believe other than the security service would have made representations to Facebook because no reasonable excuse has been given as to why our client's page has been taken down."
