This was compared to the same period in 2019, according to analysis by the Royal College of Psychiatrists.
NHS Digital data shows that 372,438 children and young people were referred in the period, which is 80,226 more than in 2019.
Data also shows 600,628 more treatment sessions were given to children and young people, up by a fifth on 2019 to 3.58 million. The number of children and young people needing urgent or emergency crisis care (including assessments for sectioning to prevent harm to themselves or others) increased by 18 per cent to 18,269.
The RCP is calling for the additional £500 million in the Government’s mental health recovery plan for frontline care. This funding is on top of the existing planned investment in mental health services set out in the NHS Long Term Plan.
Dr Bernadka Dubicka, chair of the child and adolescent faculty at the RCP, said: "Our children and young people are bearing the brunt of the mental health crisis caused by the pandemic and are at risk of lifelong mental illness.
"As a frontline psychiatrist I’ve seen the devastating effect that school closures, disrupted friendships and the uncertainty caused by the pandemic have had on the mental health of our children and young people.
"Services were already struggling to cope with the number of children needing help before the pandemic hit, and they risk being overrun unless government ensures the promised money reaches the frontline quickly."
The RCP also reports an increase of 8 per cent in the number of treatment sessions given to adults between April and December 2020 last year (1,078,539) compared to 2019, with 159,347 urgent crisis referrals, an all-time high and increase of 2 per cent on 2019.