The official magazine for Jehovah's Witnesses has described those who leave the church as "mentally diseased", prompting an outcry from former members and insiders concerned about the shunning of those who question official doctrine.

An article published in July's edition of The Watchtower warns followers to stay clear of "false teachers" who are condemned as being "mentally diseased" apostates who should be avoided at all costs. "Suppose that a doctor told you to avoid contact with someone who is infected with a contagious, deadly disease," the article reads. "You would know what the doctor means, and you would strictly heed his warning. Well, apostates are 'mentally diseased', and they seek to infect others with their disloyal teachings."

A copy of the magazine, distributed by Jehovah's Witnesses around the world, was given to The Independent by a current member of the church who has become unhappy with official teaching but is afraid to leave for fear of losing his family.

"Many like me remain associated with the Witnesses out of fear of being uncovered as an 'apostate' and ousted, not just from the organisation, but from their own friends and families," said the man, who would only give the name John. "I find I am now branded as 'mentally diseased' – giving any who discover my true beliefs free licence to treat me with disdain."

As a faith with a centralised leadership, many forms of discipline are used to counter criticism of doctrine, with punishments ranging from restriction of official duties to excommunication. Those who have been thrown out of the church often find themselves ostracised by fellow believers.

A growing number of former and current Witnesses have begun to argue that the church's use of the word "mentally diseased" to describe defectors could be in breach of Britain's religious hatred laws. A group of former Witnesses in Portsmouth have now made an official complaint to Hampshire Police about the article and police are currently investigating.

Angus Robertson, a former Witness "elder" from Hampshire, who was present at the meeting with police officers, said: "The way scripture is being used to bully people must be challenged. If a religion was preaching that blacks or gays were mentally diseased there would understandable outrage."

Critics are also considering whether to complain to the Charity Commission. The Watchtower Bible and Tract Society of Britain, which prints church doctrine in the UK, is a registered charity.

Rick Fenton, a spokesperson for the Watchtower Society, insisted last night that ostracisation was "a personal matter for each individual to decide for himself". "Any one of Jehovah's Witnesses is free to express their feelings and to ask questions," he said. "If a person changes their mind about Bible-based teachings they once held dear, we recognise their right to leave."

The offending article

* Taken from 'Will you heed Jehovah's warnings?' The Watchtower, 15 July 2011

"Jehovah, the Great Physician, tells us to avoid contact with them. We know what he means, but are we determined to heed his warning in all respects? What is involved in avoiding false teachers? We do not receive them into our homes or greet them. We also refuse to read their literature, watch television programmes that feature them, examine their websites, or add our comments to their blogs. Why do we take such a firm stand?