Big business has been accused of misleading children by producing educational materials for schools about pupils' diets which experts say are wrong and likely to encourage poor eating habits.

Questionable claims include advice to children to eat three portions of dairy products each day, to avoid refilling their water bottle from the tap, and not to eat less food if they want to lose weight while also being physically active.

In other leaflets, study aids and teaching packs, pupils are told to eat six slices of bread a day, that eating cheese 'will soon have you a lot healthier' and that soft drinks are carbohydrates, the same food type as rice, pasta and bread.

The Food Standards Agency (FSA), Britain's food watchdog, the Department of Health and the body that represents the country's 6,000 dieticians have dismissed some or many of the statements as highly selective, misleading and not based on independent evidence.

Richard Watts of the Children's Food Campaign (CFC), an alliance of health, education and children's organisations, which is assembling a dossier to send to the government, said the organisations had acted shamefully.

'These claims are wrong, misleading, taken out of context or blatant marketing, and aren't backed up by scientific advice. It's bad nutritional advice, which could give children wrong ideas about food at a very impressionable time in their lives and could also get them into some bad dietary habits.'

Organisations such as the baker Warburtons and bodies including the Dairy Council, the British Soft Drinks Association and the Food and Drink Federation collated the material.

A Dairy Council leaflet for seven- to 11-year-olds promotes eating three dairy portions a day. It says: 'You need most calcium when you are a teenager - three to four servings of milk, yoghurt or cheese will help ensure that teenagers get all the calcium they need.

'Three servings of milk, yogurt or cheese every day will provide most people with just about all the calcium their body needs.' But the FSA disagreed. It advises eating dairy products but not any specific amount.

The European Food Safety Agency, which advises the EU, has rejected the idea that eating three dairy portions a day is beneficial, stating: 'A cause-and-effect relationship is not established between the consumption of dairy foods and a healthy body weight in children and adolescents.'

Dr Alice Cotter, the Dairy Council's senior nutrition scientist, insisted that the recommendation had been 'created' using nutrient intake information produced by the Department of Health.

The FSA disagreed with most of the claims and said they were not in line with its recommendations. It said pupils should continue refilling water bottles with tap water, despite the British Soft Drinks Association producing a 'Drinks Detective' graphic which says that it is 'unsafe' and 'can lead to contamination'.

Liz Bastone, the association's spokeswoman, said: 'We advise that soft drinks bottles should be recycled after use rather than refilled ... [they] are not intended to be reused. If bottles are not washed properly, they can become a source of bacterial infection.'

The National Union of Teachers and the National Heart Forum are among those claiming that the government's guidelines to schools on how to manage such links with business are too lax.

'We are concerned that children are not exploited or misled by marketing of food products which make claims that are at best ambiguous or open to interpretation,' said Christine Blower, the union's acting general secretary.

• This article was amended on Tuesday October 21 2008. We have clarified some points in the first two paragraphs.