Calls to ban junk food adverts before the watershed have been renewed after research revealed the extent of children's exposure to the marketing of fatty and sugary products.

A study by Ipsos-Mori for the Scottish Government found that 63.5% of 11 to 18-year-olds had seen at least one food or drink marketing promotion in the last seven days, with a significant proportion viewed on television.

Almost three quarters (74%) of those sightings were for products like sweets, chocolate and cake while almost a quarter (24%) were for sugary soft drinks.

Nearly half (47%) of those surveyed said they had been influenced by marketing to buy a product in the last seven days.

With powers over broadcasting currently reserved to Westminster, Public Health Minister Maureen Watt has written to her UK counterpart Jane Ellison calling for adverts for high fat, salt, and sugar foods to be banned before 9pm.

She said: "It's clear that banning these adverts only during children's programming is not stopping under-16s from seeing them.

"If we are serious about tackling obesity, and reducing the prevalence of conditions like Type 2 diabetes, we need to make it as easy as possible for young people to eat healthy diets. That means looking seriously at the marketing of unhealthy food and drink.

"Reducing their exposure to such advertising on TV is a simple first step, and one that I believe should be taken without further delay."

James Cant, director of British Heart Foundation Scotland, said: "Over a quarter of children in Scotland are overweight or obese and dietary surveys show that children are eating too much salt, sugar and saturated fat.

"The UK Government must act now to ban junk food marketing before the 9pm watershed to help give children a stronger chance of avoiding future heart disease."

A Department of Health spokeswoman said: "We have already made progress on childhood obesity, including a total ban on the advertising of junk food during children's TV programmes and several supermarkets banning sweets at checkouts.

"We know more needs to be done - that's why we are developing a strategy to tackle childhood obesity, which we will launch in the coming months."