Apple added new rules to its iOS developer guidelines in preparation for the introduction of its Kids app category in the autumn.

Apps aimed at children under the age of 13 must include a privacy policy and require parental permission for in-app purchases and external links.

They must also avoid behavioural advertising in which ads are served based on user activity, while contextual ads must be appropriate for children.

Apps made for the Kids Category should also be pitched at specific age groups: under 5, ages 6-8 and ages 9-11. The new category was announced at Apple’s Worldwide Developers Conference in June and will arrive with the introduction of iOS 7.

The move follows a number of reports of children generating large bills after buying virtual items in mobile games without their parents’ knowledge.

In March, Apple settled a lawsuit filed by a group of parents claiming that its App Store purchasing policies allowed children to spend large amounts of money too easily when unsupervised. The company subsequently flagged freemium apps with in-app purchasing functionality to alert parents to apps that could lead their children to spend money without their knowledge.

The UK’s Office of Fair Trading is due to publish a report on children’s apps in the autumn following an investigation into whether freemium apps are pressuring or encouraging children to pay for additional content.

Many iOS developers have already added privacy policies and implemented parental permission to children’s app, in response to private feedback from Apple, according to The Guardian.

The newspaper also notes that Apple has not set guidelines on how developers can analyse activity of young users in apps but this should be covered by existing national laws, such as the Children’s Online Privacy Protection Act, recently introduced in the US.