Critics of new television food advertising guidelines say the hours should be extended because most children watch television outside the hours the restrictions apply.
The New Zealand Television Broadcasters' council has launched a new Children's Food Classification system as part of the guidelines for television adverts.
From July 1, new food or beverage adverts shown at children's viewing times must be approved under the classification system, and all adverts must comply by October 1.
The new system will restrict the advertising of certain foods.
Fight the Obesity Epidemic (FOE) spokeswoman Celia Murphy said the guidelines applied to children's programming times on TV2, TV3 and Maori TV.
On weekdays these times finished at 5pm on TV2 and 4.30pm on TV3.
"We know most children's viewing is outside these hours," she said.
Obesity Action Coalition director Leigh Sturgiss said the organisation knew from Broadcasting Standards Authority figures that more than 30 percent of children were still watching television at 8.30pm at night.
"Kids' favourite TV shows are The Simpsons, Spongebob Squarepants, Shortland Street and Home and Away. Only Spongebob Squarepants is shown during the recognised children's viewing time which ends between 4.30pm and 6pm."
FOE wanted a complete ban on television advertising of junk food before 9pm.
Obesity Action Coalition also wanted the code extended beyond television.
Websites, print media, cellphone texts, sponsorship, branding "and even curriculum materials in schools" were other ways food manufacturers reached and influenced children, Ms Sturgiss said.
Green Party MP Sue Kedgley said there was a complex method of establishing a product's suitability for screening that included a number of loopholes that allowed the industry a final say and let it ignore expertise provided by the Ministry of Health.
"I am concerned that under these guidelines, an industry which is interested mainly with commercial gain can make its own decisions on advertising to children even without the input of nutritional experts," she said.