The study by East Sussex Trading Standards found nurseries tended to incorrectly apply the requirements of healthy eating for schoolchildren and adults to one to four-year-olds. As a result, services were providing them with food that was too low in calories and fat.
Only one in five of the nurseries surveyed gave children sufficiently large portion sizes and just three out of 10 provided them with enough calories. The report's authors said there was a lack of regulation and information about nutritional eating for under-fives.
Sarah Almond, a consultant specialist paediatric dietician involved in compiling the report, said many nurseries had gone too far in banning certain foods such as chocolate or cake, since they hold some nutritional value for this age group, who have a higher need for calories and fat.
Purnima Tanuku, chief executive of the National Day Nurseries' Association, said the report highlighted that nurseries are working hard to offer nutritious food to children, but identified also a lack of information on healthy food for toddlers.
"Nationally, nurseries do face conflicting advice about food and, as there are no specific guidelines in place, it can be hard for nurseries to find the exact balance," she said.
Tanuku said many workers wanted specialist training and advice but it can be difficult to find the appropriate individuals to provide it. "Consistent advice from Ofsted and other bodies about nutritional requirements for this age group would be helpful," she said.
Neil Leitch, campaign director of the Feeding Young Imaginations at the Pre-school Learning Alliance, agreed. "The government should invest in making sure workers understand about a balanced diet," he said. "At the moment all the money tends to go to children of school age."
A spokesman for the Department for Children, Schools and Families said the Early Years Foundation Stage, which comes into force in September, would mean settings that provide food must supply healthy, balanced and nutritious meals and that the government is working to improve guidance on this.
