PRIMARY school lunches can contain twice the maximum amount of sugar four to six-year-olds are supposed to consume in an entire day, according to a report which also calls for an immediate ban on canteens offering pupils a "soup or pudding" option.

Obesity campaigners say schools must stop asking schoolchildren to choose between dessert or soup to go with their main meal as the “nutritional characteristics are not equal”. They found that this was normal practice in half of local authority areas.

They added: "Vegetables, soup and salads should receive higher priority in menu planning than puddings and the practice of offering soup or puddings should cease."

Research on the nutritional value of school lunches, which are free for all P1-P3 pupils, warned that children were at risk of consuming too much sugar with seemingly healthier options such as yoghurts typically containing three teaspoons of sugar - nearly as much as an average school pudding.

The report by Obesity Action Scotland also found that some meal combinations would result in the youngest pupils far exceeding daily recommended limits for "free sugars" - those not naturally present in fruit, vegetables and milk products. On one school lunch menu, a pupil choosing sweet and sour chicken, a lemon sponge and a strawberry milkshake would consume more than 36g of sugar - close to double the 19g maximum children aged four to six should be allowed in a whole day under guidelines from the UK's Scientific Advisory Committee on Nutrition (SACN).

It also exceeds the 24g daily limit recommended by SACN for children aged seven to 10 and the 30g limit for those aged 11 and over.

The report added: "Currently, regulations allow the nutritional value of a school meal to be averaged across the weekly offering. However this appears to mask some very high daily offerings in sugar. We strongly recommend that a third of the SACN maximum daily limit on free sugar is applied to every potential combination of school meal options. This could be implemented over time. This would ensure that every child is protected from excess sugar consumption at school."

The findings are based on a snapshot of the school meal menus posted on councils' websites during a randomly chosen week.

Glasgow and South Ayrshire council were praised for offering pupils soup and salads every day of the week, while the researchers welcomed Edinburgh City Council's decision to restrict puddings to two days a week and to serve low-sugar yoghurts.

However, they also found that 12 local authorities served puddings every day and 11 served red or processed meat - such as ham, sausages, bacon and corned beef - every day.

Two thirds of pupils in Scotland eat school lunches and the report said school food "should be an exemplar for healthy eating", with limited servings of chips, burgers, hot dogs and pizzas.

It added: "We should reduce or eliminate any ‘junk type’ food from school menus. Even if these foods are of better nutritional quality than the average ones from retail or out of home sector, their presence confirms that they are acceptable on a daily basis and exposes children to the habit of consuming these types of food."

The researchers said Scotland could learn from Copenhagen where all school food is organic and kitchens are led by chefs who design their own menus and keep costs low by baking their own bread, butchering in-house and stewing cheaper cuts of meat.

Earlier this year it emerged that Scottish councils had spent £1.3m importing chicken products from Thailand.

A spokesman for council umbrella body, Cosla, said schools do "the best job that they can within the resources they have". He added: “Regulations set out nutrient standards for school meals based on scientific knowledge and local authorities continually work to improve the nutrition and variety offered.”

A spokesman for the Scottish Government said a review of school nutritional standards is underway. 

He added: “All local authorities have a duty to provide school meals that meet strict nutritional requirements, ensuring that pupils are offered balanced and nutritious school lunches"