The Environmental Working Group, a Washington, D.C.-based health information non-profit, said its report covers more than 1,500 cereals, including 181 marketed to children.

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As part of the report, the group re-examined 84 cereals it studied in a similar report in 2011, and found that the sugar content of those cereals remained on average at 29 percent.

Some cereals had increased sugar content now compared to 2011, and none of the 181 cereals marketed to children was free of added sugars, the group found. On average, children’s cereals have more than 40 percent more sugars than adult cereals, EWG said.

"Obviously we know cereals have a lot of sugar in them," said Dawn Undurraga, an EWG consultant and a co-author of the report. "But there is a lot that manufacturers can be doing and FDA can be doing, to protect kids."

The group said one of the worst offenders is Kellogg Co.'s Honey Smacks, with 56 percent sugar by weight.

A child eating an average serving of a typical children’s cereal eats more than 10 pounds of sugar a year from that source alone, and the average daily intake of added sugar for children is two to three times the recommended amount, the EWG said.

A Kellogg official said the company has cut sugar in its top-selling kids’ cereals by 20 percent to 30 percent over time. The company said the EWG report ignores the benefits provided by a cereal breakfast, including pre-sweetened cereals.

"When you consider what constitutes a good breakfast, cereal and fat free milk pack a powerful nutritional punch, lower in fat and calories than many other breakfast choices, and including many nutrients that people might otherwise miss," said company spokeswoman Kris Charles.

The report is the latest in a push by consumer and health groups to convince food companies and regulators to cut unhealthy ingredients from packaged food products.

In March, the Food and Drug Administration proposed that added sugar content be listed in nutrition facts panels on packaged foods. But the serving sizes need to be more accurately labeled, the EWG said.

Cereal maker General Mills also has already cut the sugar content in its cereals advertised to children, on average by 16 percent since 2007, according to spokeswoman Kirstie Foster. The company's cereals advertised to children have 10 grams of sugar or less per serving, with some at 9 grams, Foster said.

The EWG said companies should not market cereals containing 6 grams of sugar or more per serving to children.