British teenagers spend more time on the internet than virtually anyone else in the world, leading them to become more unhappy and susceptible to mental health problems, a new report has found.

Nearly one in four pupils in the UK are now considered “extreme” internet users, with tens of thousands spending three times longer online than the average dwell-time of children living in the rest of the developed world.

Only Chilean youngsters spend longer browsing the web, with British youngsters spending 188 minutes per school day engrossed on their smartphones or computers.

The study - based on the OECD's Programme for International Student Assessment (Pisa) tests, which surveyed 540,000 pupils aged 15 from around the world - also found that British teenagers rank in the bottom ten for life satisfaction.