Counter-terrorism police are facing “a toxic mix” of mental health issues and online radicalisation as the country comes out of lockdown, a senior officer has warned.

Commander Richard Smith, head of the Metropolitan Police Counter-Terrorism Command, said young people in particular had been left at greater risk of online radicalisation during lockdown.

Giving evidence to the London Assembly Police and Crime Committee, he said: “One of the impacts of the pandemic has been to leave young people at greater risk of radicalisation and vulnerable people at greater risk of radicalisation online.

“It’s only as we unlock and activity then rises that we will see what that has meant for them as we get more referrals into (anti-radicalisation scheme) Prevent.

“That goes alongside what is now becoming better documented in terms of the impact of the pandemic and lockdown on people’s mental health generally.

“I’m not saying that mental illness and terrorist ideology are corroborated necessarily one way or the other, but they’re certainly not mutually exclusive.

“There’s a real toxic mix that we may see as we come out of the pandemic in terms of the numbers of people who have been at risk of radicalisation.

“I am therefore very keen to see the number of referrals into Prevent increase so that we can engage with those people and direct them onto more productive pathways.”

This week UK counter-terrorism police have teamed up with Netmums to provide advice to parents on how to spot the signs of radicalisation and where to get help.

Law enforcement are growing increasingly concerned about the number of under-18s being groomed by extremists, particularly on the far right.

In the year to March 2021, 13% of suspects arrested for terrorism offences were aged under 18, compared to 5% the previous year. Children were also the only age group to show an increase in this period.

Of the 21 children arrested up to March 2021, 15, or 71%, were linked to extreme right-wing beliefs, and the proportion has been growing since 2015.

In that year, less than 20% of under-24s were held for far right beliefs, rising to 60% in 2020.

Commander Smith said that while the number of arrests for suspected terrorist offences had dropped during the coronavirus lockdowns, this was due to a reduction in opportunities to commit crimes rather than a reduction in threat.

The terror threat for the UK has been substantial since February, and he said it remains at that level.

He told the committee: “In terms of the threat itself I have seen no reduction. Certainly as we come out of lockdown there is a sense that the tempo of activity has risen.

“We are now seeing the tempo of activity rising and therefore the tempo of our activity countering it rising commensurately.”