Health officials have named and shamed what they say are the most sugary breakfast cereals.
Some, including Kellogg's Frosties and Coco Pops, contain three-and-a-half sugar cubes or more per 40g serving, Public Health Liverpool (PHL) found.
A seven to 10-year-old's recommended maximum daily allowance is six cubes.
Kellogg's said it had recently reduced sugar in Coco Pops by 14% and added the recommended portion size for its cereals was 30g.
A spokesperson said its "long-term sugar reduction programme" had also seen sugar reduced in other cereals like Special K and Bran Flakes.
The Liverpool campaign Save Kids from Sugar has broken cereals down into "high" and "medium" sugar classifications and also recommends healthier options.
Too much sugar in a child's diet can lead to obesity, tooth decay, type 2 diabetes, heart disease and some common cancers, PHL said.
'Loaded with sugar'
Figures from the government's National Child Measurement Programme, showed more than a fifth of reception class pupils in England were classified as overweight or obese in 2015-16, with that figure rising to a third for year six children.
Almost a third of five-year-olds in Liverpool have decayed, missing or filled teeth, with two children a day under the age of 10 having to be admitted to hospital to get teeth removed, PHL said.
More than 23% of year six children are obese in Liverpool and almost 40% are overweight or obese, it added.
High sugar (between 2.4 and 3.7 sugar cubes per 40g serving):
- Coco Pops
- Coco Shreddies,
- Cookie Crisp
- Supermarket own brands including Frosted Flakes, Choco Rice and Honey Nut
Medium sugar (between 1 and 2.2 sugar cubes per 40g serving):
- Rice Krispies
- Supermarket own brands including Multigrain Hoops and Chocopops
Healthier options (less than half a sugar cube per 40g serving):
- Shredded Wheat
- Wheat Shreds
- Ready Brek
- Porridge Oats
- Alternatives such as a boiled egg, scrambled egg or toast
Source: Public Health Liverpool
Over the next three months posters and leaflets will be put in health centres, dental surgeries and hospitals in Liverpool.
The public health team will also be working with school breakfast clubs and holding events aimed at educating parents.
Parents can log on to Save Kids From Sugar to calculate how much sugar their children are consuming.
Number of 4g sugar cubes in a 40g serving
- 3.7 - Frosties (Kellogg's)
- 3.5 - Coco Pops (Kellogg's)
- 3.5 - Crunch Nut (Kellogg's)
- 2.8 - Krave (Kellogg's)
- 2.1 - Cheerios (Nestle)
- 1.5 - Shreddies (Nestle)
- 1 - Rice Krispies (Kellogg's)
- 0.5 - Shredded Wheat (Nestle), Ready Brek (Weetabix Ltd) and Weetabix
Source: Public Health Liverpool
Councillor Tim Beaumont said: "It is a myth that breakfast cereals are a healthy choice. Some are, but most are loaded with sugar. Families simply don't realise how much is in them."
Director of Public Health Dr Sandra Davies said: "Most people don't have the time to read labels when racing around the supermarket to complete their weekly shop and so we have to support them to make healthier choices."
A Kellogg's spokesperson said: "We have a long tradition of helping improve the health of the nation - whether that's adding folic acid in our foods to combat birth defects to reducing salt - and we take our responsibilities seriously.
"That's why Kellogg's is committed to providing people with less salt and sugar in our foods. Our actions will have reduced sugar from the UK's diet by more than 2,000 tonnes by the end of 2017."
A Nestle spokeswoman added that "providing clear nutrition labelling has long been a focus".
"We agree that we all have a role to play in limiting the amount of sugar children consume... and we continue to look for opportunities to make further improvements."
Liverpool-based children's charity Kind said it "fully supported" the campaign to help people "make the right choices".
"Obviously, there is a major problem with the fact that a percentage of our children live in households that are struggling financially. It is often very difficult for parents to buy the healthy option when budgets are so tight," it added.