Havant and East Hants (HEH) Mind has launched the number for 11 to 17 year olds.
It provides immediate access to safe and confidential support for young people experiencing difficulty with their mental health.
Danielle Barnes, children and young people's service manager at HEH Mind, said: “We are passionate about providing an easily accessible, confidential service for young people and glad to be launching this Freephone crisis line.
“The line is there to support young people to de-escalate emotional crisis and promote positive mental health; to prevent mental health difficulties developing into severe and enduring health issues.
“We will be working closely with schools, colleges, GPs, children and adolescent mental health services and other key services to promote the number, and together bring about positive mental health and wellbeing for young people.”
Any young person living in Hampshire or the Isle of Wight can call the number and will speak confidentially to an experienced children and young people practitioner.
At the start of the call, the practitioner will take some basic details about the caller and then will provide person-centred one-on-one support.
This involves support and intervention, listening to needs/concerns, providing support for any specific issues (anxiety, self-harm, low mood) de-escalating crisis through grounding and mindfulness techniques and emotional coping skills.
The caller can then be signposted or referred to any appropriate local service.
If the practitioner is concerned about the safety or wellbeing of a child or young person, then only after explaining this risk to the caller, will they get in touch with safeguarding organisations or urgent care.
The service has been commissioned by NHS Hampshire and Isle of Wight Partnership of Clinical Commissioning Groups (CCG) and North East Hants and Farnham CCG.
Dr Michele Legg, GP, said: “Accessing mental health services is more important now than ever.
“The pandemic has had a major impact on the lives of our children and young people – and it's important to know that easy-to-reach help is available.
“With schools and colleges closed, we know some children and young people will be struggling due to being apart from their friends, having to learn in a different way, experiencing food poverty, or unfortunately domestic issues at home.
“We also know young people may have to be dealing with relationship challenges or taking on the role of a carer – these are just some examples.
“Offering a free and confidential phone number should greatly increase the ability to access the support. You don't need to travel and can speak in privacy with a trained professional.”
The freephone number is 0300 303 1590, and is available Monday to Thursday from 3pm to 8.30pm.