At least three people in London with HIV have died after they stopped taking life saving drugs on the advice of their Evangelical Christian pastors.
The women died after attending churches in London where they were encouraged to stop taking the antiretroviral drugs in the belief that God would heal them, their friends and a leading HIV doctor said.
Responding to the BBC London investigation, Lord Fowler, the former health minister responsible for the famous Aids awareness campaign of the 1980s, condemned the practice.
"It's just wrong, bad advice that should be confronted," said the Tory peer, who chaired last month's House of Lords committee into HIV.
Jane Iwu, 48, from Newham, east London, described one case, saying: "I know of a friend who had been to a pastor. She told her to stop taking her medication - that God is a healer and has healed her."
"This lady believed it. She stopped taking her medication. She passed away," said Ms Iwu, who has HIV herself.
BBC London spoke to a second woman from east London who told of a friend who died after taking advice from her pastor who told her to stop taking her antiretroviral drugs.
Meanwhile, the director of a leading HIV research centre in east London said she had dealt with a separate case in which a person with HIV died as a result of advice from a pastor.
"I've only seen that once, but it has happened," said Prof Jane Anderson, director of the Centre for the Study of Sexual Health and HIV, in Hackney.
"We see patients quite often who will come having expressed the belief that if they pray frequently enough, their HIV will somehow be cured," she added.
"We have seen people who choose not to take the tablets at all so sometimes die."
Lord Fowler condemned pastors giving this advice, saying: "It's dangerous to the public and dangerous in terms of public health."
"It's irresponsible," he said, suggesting pastors should instead "come off the air on it, look at things much more seriously, and not give this completely wrong advice to the public".
HIV prevention charity African Health Policy Network (AHPN) says a growing number of London churches have been telling people the power of prayer will "cure" their infections.
"This is happening through a number of churches. We're hearing about more cases of this," AHPN chief Francis Kaikumba said.
AHPN said it believed the Synagogue Church Of All Nations (SCOAN), which has UK headquarters in Southwark, south London, may be one of those involved in such practices.
The church is headed by Pastor T B Joshua, Nigeria's third richest clergyman, according to a recent Forbes richlist.
When approached by BBC London, leaders of the church described themselves as Evangelical Christian pastors.
The church's website, which was set up in Lagos, Nigeria, shows photos of people the church claims have been "cured" of HIV through prayer.
In one example, the church's website claims: "Mrs Badmus proudly displays her two different medical records confirming she is 100% free from HIV-Aids following the prayer of Pastor T B Joshua."
"HIV-Aids healing" is listed on the church's website among "miracles" it says it can perform.
"Cancer healing" and "baby miracles" are also advertised.
The church's UK website promotes a monthly "prayer line" for which it says: "If you are having a medical condition, it is important you bring a medical report for record and testimony purposes."
It has posted videos on the internet showing its services in south London, in which participants who claim to have arthritis, asthma and schizophrenia say they have been healed after being sprayed with "anointing water" provided by the church.
Mary Buhari, 44 , from central London, told the BBC she had had a phone conversation with a representative of the church, in which she was told she could be cured of HIV.
"I was told they can cure any illness on Earth through prayer, including HIV," she said.
However, when asked by BBC London if it claimed its pastors can cure HIV, SCOAN responded: "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," the church added. "Doctors treat; God heals."
The recent House of Lords committee report into HIV awareness said faith groups' approaches to supporting people with HIV had improved but more needed to be done.
"It is essential that faith leaders engage with HIV as an issue and provide effective and truthful support and communication around the subject," it said.
A Department of Health spokesman responded to the report saying: "Over 60 recommendations were made and we will be responding to Parliament in the next few months."
Jane Iwu and Mary Buhari had their identities changed in this article, at their request.