Children are being almost constantly exposed to junk food advertising while using online video game websites, research has found.

The popularity of video game live streaming websites, where users log on to watch someone else complete a game, has soared in recent years. But those tuning in are being subjected to adverts for junk food and sugary drinks for 52 minutes of every hour on average.

The study by scientists at the University of Liverpool’s Institute for Population Health found that sites had 2.6 adverts an hour visible on screen for 20 minutes at a time.

A single exposure to food marketing led to an increase in consumption equivalent to an extra 37 calories, according to the study, which is being presented at the European