The Committee of Advertising Practice, which writes the rules for non-broadcast advertising, insists it doesn't want to turn advertising into a religion-free zone but says it must not stray into taboo areas.
These include using images of the crucifixion, especially if its depiction could be interpreted as mocking, or making links between religion and sex or nudity.
CAP has also told agencies to ensure no controversial posters appear close to places of worship.
The ASA is investigating complaints from the Muslim community in Birmingham, after a poster for Adidas, featuring a naked sprinter with explosives in his heels, was displayed outside a mosque.
Christopher Graham, the director-general of the Advertising Standards Authority, which enforces the CAP rules, said: "The ASA isn't in the business of trying to censor future advertising but rather we aim to ensure that the potential for hurt and offence is minimised."