The Met Police have told the BBC they are unable to charge an African pastor who accused children of witchcraft because it is not against the law.
Police said Pastor Tukala had not broken any laws
Pastor Dieudonne Tukala was arrested on suspicion of inciting child cruelty last January following an investigation by BBC Radio 4's Today programme.
Dr Tukala denies accusing children of witchcraft despite video evidence showing him doing so in a service.
Campaigners say it should be a criminal offence to demonise a child.
The BBC probe also spoke to other parents who said Dr Tukala told them to send their children back to Africa where he could pray for them to die.
And it connected Dr Tukala with a case where a child accused of being a witch was branded with an iron by his father.
So-called child witches have been murdered in some African countries.
The Metropolitan Police told the BBC it had launched a "robust and exhaustive" inquiry but said no charges have been brought after the 10-month investigation.
The BBC understands the investigation was hampered by language barriers and the reluctance of witnesses to come forward.
But, police said, it is not against the law to accuse a child of witchcraft or praying for a child to die.
Campaigners are calling for legislation to make it a criminal offence to demonise a child.