A UK branch of a Christian church has been secretly filmed trying to cast out evil spirits from a 16-year-old.
A Universal Church of the Kingdom of God (UCKG) pastor was seen reciting what looked like so-called "strong prayers" to rid the boy of a demon.
BBC Panorama was also told by a gay ex-member he was given "strong prayers" at 13 to try to make him straight.
The UCKG says under-18s are not allowed into "strong prayers" services and it does not perform "conversion therapy".
A BBC Panorama investigation has found:
The church tells its congregations it can help with mental health conditions by casting out evil spirits
The leader of the church in the UK describes epilepsy as a "spiritual problem"
The UCKG has branches around the world, including 35 in the UK, where it is registered as a charity. It says it has more than 10,000 members across the country and describes itself as a Christian Pentecostal church.
Prayers to cast out evil spirits are not unusual in the Christian world. Some churches call them deliverance or exorcisms - although the latter is not a term the UCKG uses.
Dr Joe Aldred, a Pentecostal bishop who works to bring together different Christian traditions, says: "Christians believe, I believe, there are forces for good and for evil in the world."
"Strong prayers" in the UCKG usually involve a pastor laying hands on a member of the congregation and demanding an evil spirit leaves their body. The church says it conducts the prayers at so-called "spiritual cleansing" services each week to "remove the root cause of problems".
The UCKG came under scrutiny following the murder of eight-year-old Victoria Climbie, who was murdered by her great-aunt and the woman's boyfriend.
In the week before her death in 2000, the couple had taken Victoria - who was showing signs of abuse - to a branch of the church.
A pastor said he thought she could be possessed and initially suggested she be taken to a service where "strong prayers" were performed. Later, before the service took place, the pastor told the great-aunt to take Victoria to hospital.
A Charity Commission report highlighted that "the seriousness of Victoria's condition was not fully realised or reported to the relevant authorities" in the days before she died. It said it was "concerned" the church did not have a formal child protection policy.
Following this criticism, the church introduced a safeguarding policy. Now, it promises not to perform strong prayers on anyone under 18 - or in their presence.
BBC Panorama visited a UCKG youth group service in Brixton, south London, attended by young adults and teenagers.
The undercover filming shows the pastor splitting up the group according to age.
A boy, who told the undercover reporter he was 16 at the time, is seen receiving what looks like "strong prayers" from the pastor. "My God, let your fire burn the evil spirit that hides," the pastor says.
The boy's head is held by the pastor, who then prays for the evil spirit that has entered the boy to leave.
The BBC showed the filming to Jahnine Davis, who sits on an independent government child safeguarding review panel.
She says: "Given that the death of Victoria Climbie occurred over two decades ago, based on the footage you've shared, UCKG may want to ask themselves how much have they learnt.
"Safeguarding policies are one thing but they mean nothing if they're not being implemented. They're meaningless."
In a statement, the UCKG said: "Strong prayers… are mainly performed at deliverance specific services" and "anyone under the age of 18 is not allowed" in. It said it strongly rejects the suggestion it has breached its safeguarding policy.
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With more than 30 branches in the UK, the Universal Church of the Kingdom of God claims to transform lives.
BBC Panorama spoke to 40 former UCKG members - some of them left years ago, others in the past few months.
Sharon joined the London Stratford branch when she was 19.
She says she told a pastor about her clinical depression and says he never advised her to seek professional help.
She was subjected to "strong prayers", she says - contrary to the UCKG's safeguarding policy, which says they should not be performed on people with mental health problems.
"It got to the point where I was very scared of going to those services because I was one of the targets all the time," Sharon says.
The church says "strong prayers" are not intended to be frightening or harmful and no-one should feel targeted. It also says if it is aware that "mental health concerns are involved", its "safeguarding team helps with referrals".
The BBC has also spoken to a former UCKG member, "Mark", who asked to remain anonymous because he was concerned about how the church might react. He says "strong prayers" were performed on him from the age of 13 to try to make him straight.
"When they found out I was gay, they started telling me that it was a demon causing it, that I needed to attend the Friday services where they would perform exorcisms," he says.
Mark says the prayers were performed every week for more than four years and that he tried to convince himself he was attracted to women. "I would cry myself to sleep," he says. "And it was a really hard time because the amount of self-hate was huge."
The UCKG told the BBC it does not perform "conversion therapy" and that "strong prayers are not given for matters of sexuality or gender alignment". It adds that it "welcomes people from all sexual preferences".
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At a healing service secretly recorded by the BBC where "strong prayers" were conducted, Bishop James Marques - the leader of the UCKG in the UK - tells the congregation some sickness is a spiritual problem and mental health problems are linked to evil spirits.
He told an undercover reporter: "Depression is a spiritual problem. Behind depression there is an evil spirit."
He also said, "We know that epilepsy is a medical condition but in the Bible the Lord Jesus casts out an evil spirit that was causing epilepsy. So we can understand that epilepsy in reality is a spiritual problem that has a physical, visible manifestation."
In a statement, the UCKG said "strong prayers" are never "promoted as a replacement for medical or... professional help".
Many former members spoken to by the BBC say they found leaving the church incredibly difficult.
Rachael, who left the church and now leads a campaign against the UCKG, warning of the dangers she says it poses to other young people.
"They say, 'Do you remember that assistant who was sitting here? Well, they left the church and now they are getting a divorce. Now they have cancer.'"
Sharon says she was shown a graphic video about a former member who was in a motorcycle incident that showed "all their organs out".
She adds: "They said this is what happens when you leave the church, the devil will come and take your soul."
At an event secretly filmed by the BBC, Alvaro Lima - one of the UCKG's bishops - tells followers that straight after leaving the church, "my mother became very sick, cancer in the lungs".
However, he said, she later came back to the church "and now the cancer is shrinking and she's getting better and better".
The UCKG told the BBC it "does not employ scare tactics", is "based on (voluntary) devotions" and "does not have any interest in coercion".