Online ads by Cadbury, Chewits and Squashies have become the first victims of new rules designed to protect children from products high in fat, salt or sugar (HFSS).

The Advertising Standards Authority (ASA) ruled this week that online and social media ads for the three brands were found to have breached rules prohibiting the advertising of junk food. The watchdog said the companies had not done enough to prevent under-16s seeing the content.

New rules governing children’s advertising online came into force last July, adding to rules already in place for TV ads.

In its ruling, the ASA banned Cadbury’s use of a storybook titled ‘The Tale of the Great Easter Bunny’ on its website, which featured children hunting for eggs.

Chewits had four Facebook posts banned which featured Chewie the Chewitsaurus in a number of campaigns.

And a so-called advergame app called Squashies World, where players match pairs of Squashies by flicking them towards each other, must no longer appear.

ASA chief executive Guy Parker said: “The ban on HFSS ads in children’s online media is working, but it’s important that we enforce it rigorously.

“These rulings show that we’re doing that and will help advertisers understand where we’re drawing the line.”

A spokesperson for Mondelez UK, the owner of Cadbury, commented: “We will be taking the insights and views provided by the ASA as part of this ruling and applying those learnings to our future content so we can continue to build upon our longstanding commitment to not market directly to children under the age of 16.”