A pressure group has accused the Advertising Standards Authority of effectively re-introducing the blasphemy law - abolished by Parliament three years ago - through the back door.
The National Secular Society (NSS) has protested against an ASA ban on a "mildly satirical advertisement" for ice cream, and has called on government communications minister, Ed Vaizey, to hold an inquiry into the decision.
The advertisement, which shows two priests in an embrace with the headline “We Believe in Salivation”, was ruled inappropriate by the watchdog for being potentially “offensive to Catholics” and others.
Terry Sanderson, president of the National Secular Society, said: “It seems our celebrations about the end of the blasphemy law were premature. The Advertising Standards Agency – which is elected by no-one and seems to be answerable to no-one - has reinstated the law unilaterally."
He continued: "Anyone who has seen the Antonio Federici ads knows that they are mildly humorous, in no way threatening, abusive or insulting. It is entirely wrong that these advertisements have been banned by such an unaccountable body, which needs to be reined in.”
In the letter to colaition government minister Ed Vaizey, the NSS adds: “We have now reached the stage where any reference to religion that is not completely reverential is immediately branded as 'offensive' and therefore unacceptable. This is an intolerable threat to freedom of expression that must be challenged."
“We ask that you instigate an enquiry into the ASA’s oversensitive approach to advertising with a religious theme. It is getting completely out of hand when something as mild and humorous as these ice cream advertisements is banned from public view on such spurious grounds,” the organisation adds.
Previous advertisements by the same ice cream company have also been banned, including one showing a pregnant nun.
The Advertising Standards Authority is the UK's independent regulator of advertising across all media, including TV, internet, sales promotions and direct marketing.
It declares: "Our role is to ensure ads are legal, decent, honest and truthful by applying the Advertising Codes."
The ASA has yet to respond to the complaint about the basis of its ruling.