An ad featuring the strapline 'Is a premature death so tempting? next to a picture of a young girl eating a cupcake sparked anger in the food industry when it was first run in women's magazines in February.
The row has now spread to parenting website Mumsnet, with hundreds of mums attacking the ad.
One poster on the site, who labelled the ad "patronising scaremongering", said: "The message eat a cupcake and you will die is not helpful in the slightest." Another called it "patronising, off-putting and as educational as Eastenders".
It is understood that up to £500,000 of public money was spent on the ads, which were created by charities Diabetes UK, Cancer Research UK and the British Heart Foundation, and run as part of Change4Life, the Government's campaign to fight obesity.
A spokeswoman for the Department of Health defended the ad and would not rule out similar campaigns in the future.
"This does not use scare tactics," she said. "It reinforces Change4Life advertising succinctly and in straightforward language."