The South African Post Office has been banned from inviting children to write to Father Christmas after a complaint.
The Post Office argued the Father Christmas ad was "harmless"
The Post Office had run a television advertisement encouraging children to write to a special address with their wish list of presents.
But the South African Advertising Standards Authority (ASA) said the ad exploited the Father Christmas myth and the "natural credulity" of children.
It concluded the ad breached the county's advertising standards code.
The ASA took action after journalist Andrew October from Cape Town made a complaint.
He said the Post Office's ad encouraged "a falsehood that could break the fragile spirits of the already disillusioned youth of South Africa".
Unless the Post Office was willing to give all the children who wrote to the address the presents they wished for, the ad should be banned, he added.
The ASA agreed with Mr October, and also noted that an additional aspect of the Father Christmas myth was the belief that only good children got presents on Christmas Day.
Any child who wrote to the address, but did not receive the presents they wished for, may feel they were being punished for naughtiness, the ASA found.
This could prove "extremely upsetting" for them, it added.
Advertising agency Lobedu Leo Burnett, responding on behalf of the Post Office, argued that the ad was "harmless" and that the tradition of writing to Father Christmas is well known and supported by many parents.
It also said that living in a "fantasy world" was a part of the growing up process, although it said small gifts would have been sent to children writing letters whom the Post Office had felt were genuinely in need.
And if this ruling was not damaging enough for Father Christmas, residents in his traditional home in Finnish Lapland are concerned that little snow has fallen since October.
This could mean no white Christmas for the thousands of tourists who travel there each year.