The police force that issued a teenager with a court summons for calling Scientology a cult could face a judicial review over the legality of its policing guidelines.
Although prosecutors last week declined to take the 16-year-old to court, freedom of speech campaigners are to ask City of London police to explain how the initial decision to issue the summons was made.
Campaigners said they would call for a judicial review if it is found that the force's guidelines for policing demonstrations led officers to confront the schoolboy.
If it emerges that the policy relates only to anti-Scientology demonstrations, a complaint could be lodged with the Independent Police Complaints Commission instead.
Shami Chakrabarti, the director of the civil liberties organisation Liberty, which spearheaded the teenager's defence, said: "We want to know who gave the instruction to issue this summons.
"Curtailing people's freedom of speech is a very serious issue and it's important to know whether this is part of the force's policy or a decision relating specifically to the Church of Scientology. There is the possibility of a complaint to the IPCC or a judicial review."
Chakrabarty said she was concerned the police action could have a "chilling effect" on other protesters who wanted to express their opinions.
"Some people are very easily intimidated and will be put off exercising their right to free speech by the thought that they may face court action over it. We have to defend that right and show how wrong the police were in issuing this summons," she said.
The teenager's plight came to public attention last week when he posted a message on an anti-Scientology forum asking for advice after taking part in a protest outside the church's headquarters near St Paul's Cathedral on May 10.
A video and photos emerged showing a City of London police officer at the peaceful demonstration advising the young protester to take down a placard that read "Scientology is not a religion it is a dangerous cult".
He refused, citing a high court judgment in which Scientology was described as a "dangerous cult". After taking advice from a senior officer, the policewoman issued a summons and confiscated the sign, saying it was an incitement to religious hatred.
A simultaneous demonstration outside a Scientology office in London's West End featured protesters waving similar signs, but the Metropolitan police did not confiscate them or issue any summonses.
Two years ago, the City of London police attracted criticism when it emerged that more than 20 officers, ranging from constable to chief superintendent, had accepted gifts worth thousands of pounds from the Church of Scientology.
At the opening of the church's headquarters in 2006, the City of London chief superintendent, Kevin Hurley, praised Scientology for "raising the spiritual wealth of society".
Last year, a video praising Scientology emerged featuring Ken Stewart, another of the City of London's chief superintendents, although he is not a member of the group.
Scientology was founded by the science fiction writer L Ron Hubbard in 1952 and espouses the idea that humans are descended from an exiled race of aliens called Thetans. The church continues to attract controversy over claims that it separates members from their families and indoctrinates followers.
