Nearly a quarter of UK five-to-seven-year-olds now have their own smartphone, Ofcom research suggests.

Social media use also rose in the age group over last year with nearly two in five using messaging service WhatsApp, despite its minimum age of 13.

The communications regulator warned parental enforcement of rules “appeared to be diminishing.”

It also said the figures should be a “wake up call” for the industry to do more to protect children.

In its annual study of children’s relationship with the media and online worlds, Ofcom said the percentage of children aged between five and seven who used messaging services had risen from 59% to 65%.

The number on social media went up from 30% to 38%, while for livestreams it increased from 39% to 50%. Just over 40% are reported to be gaming online - up from 34% the year before.

Over half of children under 13 used social media, contrary to most of the big platforms’ rules, and many admitted to lying to gain access to new apps and services.