Seriously ill patients suffering from conditions including cancer and HIV are being encouraged by some Evangelical Christian churches to depend on prayers rather than pills.
Worshippers in London, Manchester and Glasgow have stopped taking life-saving drugs after being persuaded about the healing powers of God, according to research by the African Health Policy Network (AHPN).
A BBC London investigation yesterday revealed that at least three women with HIV have died after they stopped taking medication on the advice of their pastors.
Francis Kaikumba, chief executive of AHPN, said a family member committed suicide last year after being convinced by a church he did not suffer from a mental health problem. The man's mental health deteriorated after he stopped taking his medicine after taking guidance from the pastor.
Mr Kaikumba said: "This is a national concern... It is about spiritual healing being the preferred option for every condition and in some cases people being told that medication will damage the affects of the prayers. We have found very vulnerable people in London, Glasgow and Manchester being offered one-stop solutions to very complex issues such as diabetes, TB [Tuberculosis], cancer, as well as housing and immigration problems. This is not just a trend in the UK, it is happening on a much wider scale in Africa."
The charity said it believed the Synagogue Church of All Nations, which has its UK headquarters in south London, may be involved in such practices. The church's website shows videos and photographs of people the church claims to have been "cured" of HIV, cancers, leg ulcers and fractures.
Naomi Phillips, head of public affairs at British Humanist Association, said: "In a free society, people have the absolute right to believe what they want. However, when those in positions of influence, particularly over very vulnerable people, are promoting false cures through religious practice and even encouraging people to turn away from proper medicine, then more needs to be done."
A spokesman for the Church of All Nations told BBC London: "We are not the healer. God is the healer. Never a sickness God cannot heal. Never a disease God cannot cure. We don't ask people to stop taking medication. Doctors treat; God heals."
The website of The Universal Church of the Kingdom of God, which originated in Brazil and has its UK headquarters in north London, says "[it] does not claim to heal people, but believes that God can heal through the power of faith."