People in crisis were referred for urgent or emergency mental health support at the Lincolnshire Partnership Trust more than 800 times in just a month, figures show.
The coronavirus pandemic has contributed to more people reaching crisis point nationally because they are not receiving the help they need in time, according to mental health charity Mind.
NHS Digital data shows in May, crisis teams at Lincolnshire Partnership NHS Foundation Trust received around 865 urgent new referrals, including 645 potentially life-threatening emergency cases.
Some 20 children were among those needing emergency help, the figures show.
At the end of the same month, there were roughly 410 people already subject to crisis care plans managed by the trust.
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 the Lincolnshire Partnership Trust's crisis teams in May were up from the 360 recorded in May 2020 and higher than the 205 received in 2019.
Leila Reyburn, from Mind, said the pandemic had affected the scale and severity of mental health problems across the nation, with more people experiencing issues for the first time and those with pre-existing problems requiring more urgent and acute treatment.
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."
Across England, there were more than 28,000 emergency or urgent referrals made in May this year, up from around 25,700 in 2020 and 26,500 two years earlier.
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-19 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.”