A third of primary school children are not getting enough sleep, putting them at risk of obesity, experts have warned.

A new poll for the British Nutrition Foundation (BNF) found that 43% of adults sleep less than the recommended minimum of seven hours a night, while 32% of primary and 70% of secondary school pupils sleep for less than nine hours - the absolute minimum they should get.

The survey covered more than 6,000 primary and secondary school children and just over 1,500 adults.

It also found that 80 per cent of adults and 50 per cent of secondary school students reported waking up at least once during the previous night.

Screens may be to blame for disturbed sleep, the poll suggests, with 59 per cent of secondary school pupils, 50 per cent of adults and 49 per cent of primary school children saying they used a screen before bed on the previous night.