Restrictions on television junk food adverts do not properly protect children, say researchers.
The restrictions are aimed at tackling child obesity
A report by Which? magazine concludes children are still exposed to adverts promoting foods with high sugar, salt and fat content.
It found 12 of the 20 programmes most popular with under-10s were not covered by the current restrictions.
However, the advertising industry rejected a call for a total ban before 9pm as too simplistic.
Which? argues that such a hard line approach on any product loaded with fat, salt or sugar is the only effective way to protect children.
A recent report warned that without sustained action 26% of children and young people will be obese by 2050.
The Which? analysis of TV viewing figures showed commercials for Mars Planets, Kinder Bueno, Milky Way, Smarties and Twix were being broadcast during shows popular with youngsters.
The new rules, introduced earlier this year, impose curbs on adverts during shows where child viewers make up a high percentage of the total audience.
But Which? found high profile shows watched by thousands of younger people fell outside the restrictions because they were also popular with many adults.
These included: The X Factor, Ant and Dec's Saturday Night Takeaway and New You've Been Framed.
Miranda Watson, from Which?, said: "The only way to shield children from TV ads for unhealthy foods is a 9pm watershed."
Richard Watts, of the pressure group Sustain, said: "We are in the middle of a children's health crisis.
"Parents have a role to play in improving their children's diet, but they need some support in exercising that responsibility, and part of that is not subjecting their kids to wall-to-wall junk food advertising before 9pm."
Julian Hunt, of the Food and Drink Federation which represents manufacturers, said the research on which the new restrictions was based showed the effect of advertising was tiny.
He said: "The UK is now one of the most heavily regulated markets in Europe, and the new rules should be given time to take effect.
"Calls for bans on advertising around programmes popular with families are completely premature."
Ian Twinn, from the Incorporated Society of British Advertising, said: "if you ban advertising no-one gets thinner or fitter as a result.
"In Sweden there is no advertising to children, and the children there are as fat as in the UK."
The Which? findings are based on TV viewing figures for ITV1, Channel 4 and Five for the first two weeks of September.