The Metropolitan Police's decision to compel officers and staff to declare if they are or have been Freemasons allows the force to create a "black list" and is an "institutional signal of suspicion", the High Court has been told.
The Met announced in December that membership of the Freemasons or similar organisations would be added to its declarable associations policy,
This means officers and staff were required to declare membership "past or present" of any organisation that is "hierarchical, has confidential membership and requires members to support and protect each other".
Two serving police officers who are Freemasons, and three bodies representing Freemasons in England, Wales, the Isle of Man and the Channel Islands, are seeking to take legal action against the force over the decision at the High Court.
At a hearing in London, barristers for the individuals and the United Grand Lodge of England, the Order of Women Freemasons and the Honourable Fraternity of Ancient Freemasons asked a judge to allow the challenge to proceed and to temporarily suspend the policy pending the full hearing of the claim.
Barristers for the Met have said that the challenge should be thrown out as it is "not arguable".
In court on Wednesday, Claire Darwin KC, for the Freemasons, said: "The aim of the Metropolitan Police is to create a black list of Freemasons that they will then use to assess risk.
"If the Metropolitan Police were creating a list of anyone else who held a particular religion or belief, and then cross-checked promotions against that list, it would be denounced, rightly, as a discriminatory black list."
The barrister told the court that officers and staff were also obliged to report colleagues who had not declared their Freemasonry, but no action had yet been taken against anyone who had failed to declare membership.
In written submissions, Ms Darwin said the decision breached Freemasons' human rights and was based on "limited, opaque and heavily perception-driven" evidence.
Ms Darwin continued that 26 intelligence reports were made to the force in 2025 where Freemasonry was "mentioned", and 16 which were said to be "adverse or potentially adverse", but these had not been disclosed.
She later said: "The defendant appears to rely on 'public narratives' or 'perceptions' as a justification for introducing and maintaining the requirement.
Ms Darwin continued: "Those public narratives are not articulated, but it is to be inferred that they relate to long-standing conspiracy theories and/or prejudicial tropes about Freemasons."
The barrister also said: "This is not a neutral 'administrative' request; it is an institutional signal of suspicion liable to colour perceptions and treatment of Freemasons."
James Berry KC, for the Met, told the court in his written submissions that 397 officers and staff had made declarations under the policy.
He said that declarations are "made and held confidentially" and that officers and staff "are free to become or remain Freemasons".
The barrister continued that claims that the decision breached officers and staff's human rights were "without merit" and that fears of stigmatisation are "not supported by the evidence".
He said: "Requiring officers to disclose true information about substantial associations in their life, relevant to vetting and assessments of conflicts in connection with police service, is designed to secure public confidence in every Metropolitan Police officer, and therefore the proper exercise of the functions of a constable."
Mr Berry continued: "The claimants are wrong to state that the defendant has no power to impose the disclosure requirement. The claimants exaggerate the impact of the declaration requirement.
"The impact is, in any event, justified and proportionate. The public confidence imperative in favour of officers and staff confidentially declaring their Freemasonry strongly outweighs the claimants' desire to keep membership secret."
He also said: "It does not appear to be disputed that there is a stigma associated with Freemasonry, which is long-standing, complicated and contested by the claimants.
"The defendant is not responsible for the stigma; but the defendant is responsible for addressing it, in connection with the exercise of police duties and functions by the defendant's officers and staff, and for positively maintaining public confidence in the impartiality and transparency of the Metropolitan Police."
The hearing before Mr Justice Chamberlain is due to conclude later on Wednesday.
