Young children are missing out on key vitamins and scoffing down too many calories and far too much salt, experts have warned.
Almost all of the children (99%) in a study by researchers at University College London (UCL), had more salt in their diet than the 0.5g daily recommended by the Department of Health.
Many had three times too much.
The researchers cautioned that too much salt at a young age could "set taste preference for the future", putting children at risk of high blood pressure and strokes in later life.
They also urged parents to follow government guidelines on giving children up to the age of five supplements to boost levels of iron and vitamin D, after finding youngsters were woefully lacking in essential vitamins.
The study, published in the British Journal of Nutrition, examined data for 2,336 children taken from one of the UK's largest dietary datasets for toddlers, the Gemini twin birth cohort.
Parents of the 21-month-olds filled in three-day food diaries and the UCL researchers analysed the results.
According to the study, protein intake among almost all children was nearly three times higher (40g) than the recommended 15g, while fibre intake was 8g - half the recommended amount.
Vitamin D intake, including the small number of children (7%) already given supplements, was less than half that recommended by the Department of Health.
Most children (84%) did not meet the recommended amount of seven to 8.5 micrograms a day - with the average intake being just 2.3 micrograms a day - and only 30% of children got enough iron (recommended to be 6.9 micrograms per day).
Hayley Syrad, from UCL's department of epidemiology and health, said: "The research suggests that the current diets of young children in England are a cause for concern.
"We know that dietary preferences and habits are established during the first two years of life and that what we eat in early life can have an enduring impact on our health."