Intentional self-poisoning or self-harm resulted in children being admitted to Bedfordshire Hospitals Trust at least 151 times last year, figures show.
Mental health charity YoungMinds said it is "deeply concerning" that hospital admissions for young people self-harming rose to record levels nationally amid the coronavirus pandemic.
NHS Digital data shows there were between 151 and 157 admissions for self-harm or self-poisoning for children aged nine to 17 at Bedfordshire Hospitals NHS Foundation Trust in 2020-21.
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In 2019-20, there were around 187 hospitalisations.
And at least 185 admissions were recorded between April and November last year – in the first two-thirds of 2021-22.
Admissions are rounded to the nearest five, and exact numbers are not available when there are fewer than eight cases a year, to protect patient identity.
There is no further breakdown between the two hospitals - Bedford and Luton & Dunstable.
Across England, at least 20,520 hospital admissions for self-harm or poisoning for youngsters aged nine to 17 were recorded last year.
This was up from 20,400 the year before, and the highest number since records began in 2007-08.
YoungMinds said many young people find it hard to ask for help until they reach a crisis point, and that even before the Covid-19 crisis began they struggled to access support.
Olly Parker, head of external affairs at the charity said: “It is deeply concerning to see that hospital admissions for self-harm admissions have risen to their highest since records began.
“The reasons why young people self-harm are often complex, but we know that traumatic experiences at a young age – like bereavement, bullying or abuse – can have a huge impact.
“The Government must invest in a network of early support hubs across the country so that all young people who are starting to struggle with their mental health are able to get support."
Of the admissions last year at Bedfordshire Hospitals Trust, between 126 and 132 were for self-poisoning – excluding alcohol – and between 26 and 32 were for self-harm.
The NSPCC said the pandemic had been "extremely challenging" for young people – either for those isolated in abusive homes, or those adjusting to a different way of learning.
A spokeswoman said some children use self-harm to cope when they are overwhelmed with difficult feelings and emotions.
She added: “While children are incredibly resilient the pandemic has understandably taken a toll on their emotional wellbeing, which is why the NSPCC want to see the Government invest in an ambitious plan for children that includes more mental health support in both the classroom and the community.
"This will ensure children can access the mental health support they need before things reach crisis point.”
The Department for Health and Social Care said it is committed to supporting the mental wellbeing of young people, including through early intervention and treatment.
A spokeswoman said: “We are training a new dedicated mental health workforce for schools and colleges with mental health support teams to cover an estimated 3 million children and young people by 2023, and this will include support for pupils who are self-harming."