Fast food outlets will come under pressure this week not to sell junk food to children, with the government pressing local authorities to take a tougher stance.

Shona Robison, the Health Minister, signalled yesterday that she wanted licensing boards to restrict the number of burger vans allowed to set up shop near schools in an effort to encourage healthier eating.

Tanning salons, off licences and betting shops could also be discouraged in impoverished areas to promote a "healthy mix of shopping outlets", the minister said.

Her proposals come after Scotland was revealed last week as the world's second most obese nation behind America, and will form the basis for forthcoming discussions with local authorities.

The proposals were welcomed by Pat Watters, president of the Convention of Scottish Local Authorities, who said: "Councils are always looking at diversity and quality of retail and most try to get a balance. We are committed to looking at this and we fully laud the proposals, but some of the technicalities will need to be looked through. Market forces have an effect."

Alarm at rising obesity levels among children and young people has already prompted a ban on vending machines in schools but campaigners have been pushing for action to be taken outside school gates, as many pupils still go to fast food retailers for lunch.

Schools could also consider an English-style "lunchtime lock-in", forcing children to remain within the school during the lunch hour, the minister said in an interview with a Sunday newspaper. The idea has already been adapted at St Mungo's High in Falkirk, where staff said it has led to improved behaviour among children.

The NHS-run slimming programme, Counterweight, would also be extended to overweight children, ensuring they and their families are given proper advice on diet and healthy lifestyle choices.

Glasgow has been leading calls for a ban on burger vans, that have thought to have contributed to a sizable drop in the number of children eating school dinners.

However, in a further blow to the drive towards healthy eating, a survey published today shows that price and convenience still dictate most people's choices when shopping for food.

Price was the number one priority for 32% of the 7000 people questioned for BBC Countryfile magazine.

Four-in-10 respondents said they would not buy locally produced food if it was too expensive.

Supermarkets were the most popular places to shop for local produce among 26% of people polled.