In a letter to Caroline Flint, public health minister, the coalition of groups call for a reassessment of the Committee of Advertising Practice (CAP) code for non-broadcast advertising and marketing.
The new rules, which apply to websites and other forms of advertising, do not enforce food companies to differentiate between healthy and non-healthy food and will not protect children from crafty marketing tricks, the groups argue.
The group also condemned the use of online games for children on the websites of fast-food outlets such as McDonalds and Burger King.
"The rise in childhood obesity and diet-related disease needs to be addressed urgently," Which? food campaigner Miranda Watson said.
"The CAP restrictions were an opportunity to finally make progress, but they have fallen well short of the mark."
Other organisations involved in the campaign include are the Children's Food Campaign, Diabetes UK, National Consumer Council, National Heart Forum and netmums.com.
"So many organisations feel incredibly strongly about this issue. The government needs to step in, tighten the existing CAP codes and ensure that those areas that fall outside the codes are tackled," Ms Watson added.
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