The watchdog said it had “particular concerns” about TikTok’s approach to age assurance, nearly a year after child-safety measures under the Online Safety Act came into force.

According to Ofcom, TikTok’s method of estimating users’ ages may have failed to correctly identify “a significant proportion of children”, potentially exposing them to harmful content.

The regulator stressed that it had not reached any conclusions.

However, if TikTok is found to have breached its obligations, it could face a fine of up to £18m or 10 per cent of its qualifying worldwide revenue, whichever is higher.

The harmful content covered by the rules includes material related to disordered eating, self-harm, suicide and pornography.

In the most serious cases, Ofcom can also seek to have websites blocked or restricted in the UK.

Ofcom said, “This investigation will seek to establish whether there are reasonable grounds to believe that TikTok has failed, or is failing, to comply with its legal obligations … including by using age assurance that is highly effective at correctly determining whether or not a particular user is a child.”

TikTok said users are required to enter their date of birth when creating an account.

“We also use technology that looks at information, often called ‘signals’, to check for indicators that someone may not meet our minimum age requirement,” it adds.

Meanwhile, the UK government is preparing to introduce a social media ban for under-16s early next year, a move that is expected to increase scrutiny of the methods technology companies use to verify users’ ages.