Anomalies contained in new rules limiting junk food advertisements during children’s programmes mean that cheese and porridge cannot be promoted during Bob the Builder but fast-food restaurants have free rein to advertise during Dancing on Ice or The X Factor.

The rules, published yesterday by Ofcom, the broadcast regulator, have left parents, health campaigners, food manufacturers and the advertising industry all unhappy.

The consumer watchdog Which? predicted a rush of advertisements for oven chips, chicken nuggets and sugary breakfast cereals during early-evening family viewing.

There is concern that while characters such as Shrek or Postman Pat cannot be used to endorse food products on TV, companies can continue to use brand characters, such as Tony the Tiger on Kellogg’s Frosties.

And there is nothing in the rules to prevent a company such as Burger King or Cadbury advertising its brand rather than a product.

The anomalies arise because of the formula devised by the Food Standards Agency to decide what is a “good” or “bad” food. A food classified as “high in saturated fat, salt or sugar” scores 4 points or more, while a drink classified as “high in saturated fat, salt or sugar” scores 1 point or more.

Every food is scored according to a 100g portion. This means that foods which are normally eaten only in small amounts — such as cheese, raisins or Marmite — are treated in the same way as a large burger from a fast-food outlet.

Campaign groups were disappointed that Ofcom rejected a 9pm watershed on junk food adverts. However, they were pleased that it had recognised the need to target older children under 16. Junk food adverts cannot be shown during programmes such as Friends and Hollyoaks, which are cult viewing among young teenagers.

The new rules for programmes aimed at children aged 4 to 9 will come into force on April 1. The rules for programmes aimed at the under16s will come into effect on January 1 next year.

Current advertising campaigns can continue on TV until the end of June, although dedicated children’s channels have until December 2008 to phase in the changes.

Ofcom estimates that the total impact on broadcasters’ revenue could be as much as £39 million in the first year.

Last night industry sources conceded privately that they could live with this shortfall as they expected junk food advertising to remain on screen.

Currently, the commercial broadcasters spend £40 million on children’s television. There are concerns that, with advertising falling, investment in children’s television will plummet.

Ofcom rejected a blanket ban, saying that this would have a draconian impact.

The music channels and the broadcasters that target children will be the most severely hit. Time Warner, the owner of Cartoon Network, is expected to lose about 4 per cent of revenues; by contrast, the impact on ITV and Channel 4 will be less than 1 per cent.

Melanie Leach, director general of the Food and Drink Federation, slammed the extension of new rules to under16s as “disproportionate”. She is also vehemently opposed to the formula to decide if a food product is healthy or unhealthy.

There is concern that firms have not been given incentives to reformulate products. Baby-bel cheese, for example, has introduced a range that is 30 per cent lower in fat but still faces a ban under the formula.

Tessa Jowell, the Culture Secretary, said that the Government would take further action if necessary. But she added: “It is important to remember that there is no single magic bullet solution. A healthy diet, regular exercise and good education about food and lifestyle all have a role to play in tackling childhood obesity.”

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