Adverts featuring a huge blob of Marmite left children "terrified" and suffering nightmares, the Advertising Standards Authority (ASA) has revealed.
A crowd is shown either running away from or towards the blob
The TV adverts show scenes reminiscent of 1950s science fiction film The Blob.
Six viewers complained that their children, aged between two and three, had been terrified by the commercials.
Marmite makers Unilever Bestfoods said it would take the ads off programmes for young children but the ASA banned them from all children's programming.
One commercial shows a woman screaming and running terrified out of a supermarket and a young couple running away from a large brown blob.
A crowd appears, some running away, others diving into the blob and eating it.
The commercials end with the Marmite slogan: "You either love it or hate it."
Viewers complained that the adverts had caused "distress" to their children after being broadcast around programmes aimed at youngsters.
A spokesman for the ASA said: "All the viewers said that their children had been terrified by the advertisements. Four said their children refused to watch television after seeing it and a further two said their children had nightmares as a result."
But the Broadcast Advertising Clearance Centre (BACC), which vets commercials before they go out, defended its decision to allow the adverts for the yeast extract spread.
They represented "very mild horror that was clearly over the top and comical", it said.
Unilever Bestfoods argued that the ASA's decision was "unnecessarily prescriptive" because only very young children had been affected by the advertisements.