The advertising watchdog said in a bulletin on its website that it subjects all campaigns to three "acid test" questions after a complaint: whether the advertisement will offend most people who see it; whether it will so deeply offend a few that their interest should prevail over the charity's right to reasonable free expression; and whether people not offended by the advert should be prevented from hearing what the charity has to say.
The ASA chose recent campaigns by Save the Children, the Children's Society and the NSPCC to illustrate its methods.
Complainants said that the campaigns could upset children.
Save the Children's campaign was banned because it was unclear from the envelope that it was from a charity.
However, the Children's Society's campaign escaped a ban because it was clearly marked as a charity mailing, and the NSPCC's because it was addressed to adults.