The ad, produced by the Universal Church of the Kingdom of God (UCKG), contained a testimonial from a woman whose son had been near death.
She thanked the UCKG for its spiritual support through to his recovery, and mentioned the use of "blessed oil".
A footnote advised people, in accordance with the CAP Code, that the spiritual advice should be taken as a complement to scientifically proven treatment.
The British Humanist Association and two members of the public challenged whether the UCKG could substantiate the implied medicinal claim.
The ASA felt the ad was irresponsible and could discourage people from obtaining qualified medical advice.
It also felt the reference to the CAP Code was an implied endorsement of the ad.
UCKG asserted the testimonial stated the individual had received only "spiritual support" and no other help was mentioned.
It further added that the CAP Copy Advice team had recommended the term as an alternative to medical or physical help.
The advertiser pointed out the disclaimer made clear that any support offered was not to be taken in lieu of professional medical treatment and instruction.
It added that the reference to the CAP Code had been included following the guidance received from the CAP Copy Advice team.
The ASA noted the testimonial explained the woman’s son’s condition and ensuing hospital treatment.
But it also highlighted that UCKG had provided "blessed oil" to anoint the child who had subsequently recovered.
On this point the watchdog felt the ad implied that the oil was integral to the boy’s recovery and was thus likely to mislead.
It also felt the reference to the CAP Code would be seen to endorse the ad and on this point was also likely to mislead.
The ad must not appear again in its current form.