The pandemic has contributed to more people reaching crisis point nationally because they are not receiving the help they need in time.
People in crisis were referred for urgent or emergency mental health support at Hertfordshire Partnership University Trust more than 600 times in a month, figures show.
NHS Digital data shows in May, crisis teams at Hertfordshire Partnership University NHS Foundation Trust received around 665 urgent new referrals, including 15 potentially life-threatening emergency cases.
Some 15 children were among those needing emergency help, while another 160 youngsters were the subject of urgent referrals.
Crisis teams, which offer an alternative to hospital admission where appropriate, are usually made up of experienced mental health staff and may include psychiatrists, social workers and nurses.
They step in to help where someone is considered to be experiencing a mental health crisis and may otherwise be admitted for inpatient support.
New referrals made on an urgent or emergency basis to Hertfordshire Partnership University Trust's crisis teams in May were up from the 535 recorded in May 2020 and lower than the 790 received during the same month in 2019.
Leila Reyburn from mental health charity Mind said the pandemic had affected the scale and severity of mental health problems across the nation.
Calling for the Government to provide sustainable funding for NHS mental health services and community-based initiatives, she added: "Even before the pandemic, many people weren't getting the right support.
"The increase in urgent and emergency crisis referrals indicates people are not getting the support they need in time, and are reaching crisis point as a result – including self-harming, experiencing psychosis and suicidal thoughts.
"Many services in the community have been forced to restrict what they can provide, or even close altogether.
"When people do not get the right mental health support early on, they are far more likely to end up in crisis."
Nationally, there has also been a stark rise in emergency referrals for children since the pandemic hit, from 644 in 2019 to 943 this year.
A Government spokesperson said: “Covid has affected everyone in the UK and we recognise it has had a disproportionate impact on certain groups of people.
“Throughout the pandemic, community and crisis services have continued to provide support, including by using digital and face to face appointments.
"As we look beyond the pandemic, we remain committed to expanding and transforming mental health services in England, backed by £2.3 billion a year by 2023-24.
“Our mental health recovery action plan – supported by £500 million – will ensure we offer the right support in 2021-22 to help people with a variety of mental health conditions.”
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