Publishing results of a survey of more than 100 foods for babies and toddlers, the Children's Food Campaign said Farley's rusks were 29 percent sugar and some Cow & Gate toddler biscuits contained trans fats, which have been linked to heart disease.
"The results of this survey are staggering," said Christine Haigh, spokeswoman for the CFC.
The CFC survey found that 100g of Farley's Original Rusks, made by Heinz, contained 29g of sugar, more than that contained in the same weight of some chocolate digestive biscuits.
Heinz Toddler's Own Mini Cheese Biscuits contained 7.3g of saturated fat per 100g, more than the 6.7g in an equal weight piece of a McDonald's quarter pounder burger with cheese.
Cow & Gate, which makes a range of baby and toddler formula milks and foods, responded to the survey by halting production of its baby biscuits.
"In discussion with the Food Standards Agency we have already taken the decision to discontinue our baby biscuits, when we became aware of the presence of hydrogenated fat, which contains a very small amount of trans fats," a spokeswoman said.
"Farley's Rusks have been enjoyed by generations of babies, and some adults too, for 120 years," it said in a statement. "Enriched with vitamins and minerals, the unique Farley's Rusk recipe has remained virtually unchanged."
The CFC, part of food and farming campaign group Sustain, said it examined the nutritional content of 107 baby and toddler foods available in UK supermarkets in March.
It found only half the products were low in saturated fat, salt and sugar, as defined in Britain's Food Standards Agency guidance.