In response to results of a survey of more than 7,000 young people, Young Minds has launched a campaign called Act Early, which is urging a new strategy that prioritises early intervention on mental health.
Yount people were asked about mental health support for issues ranging from exam stress at school to coping with trauma.
This found that two thirds (67 per cent) had been unable to access support when they first needed it.
More than three quarters (78 per cent) of those surveyed said they have to manage their mental health by themselves as they could not find help, however, just 17 per cent said they felt confident doing this on their own.
The charity is concerned that mental health problems among young people can escalate if not addressed quickly.
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"These results show how hard it can be for young people to get help when they first start to struggle - and we know that the impact of leaving it too late can be devastating," said Emma Thomas, chief executive of Young Minds.
Thomas added: "We're seeing welcome investment in NHS mental health services, and some positive initiatives in schools, but with rising demand, it won't be enough to meet the need.
"It's vital that we ensure that the right help is available when young people first need it.
"We know that local support, through youth clubs or local charities, can be incredibly helpful - but this is something only a small number of young people are able to get.
"It's far better to make sure young people can get help early, rather than add to the numbers needing specialist support."
The charity survey asked young people what factors were impacting negatively on their mental health.
Pressure to do well as school was cited by 77 per cent, worries about appearance by 69 per cent and family problems by 62 per cent.
Dealing with traumatic incidents was mentioned by almost half (46 per cent) of respondents.
The charity highlights the case of 22-year-old Nikki who describes how she struggled to access support as a child.
She was first referred to child and adolescent mental health services (CAMHS) at the age of 14 to deal with issues including trauma, bullying and family problems, but was told she failed to meet the threshold for support.
"There were so many issues impacting my mental health, so it really broke my confidence when they told me I wasn't ill enough for treatment," said Nikki.
"By the time I finally got an appointment, I had already reached crisis point.
"It would have made a huge difference if I had been offered preventative support when I first reached out for help."
In addition, a quarter (27 per cent) said spending too much time on social media impacts their mental health, and a similar proportion (24 per cent) worry about current affairs.
Thomas added: "The government must also take action to address the factors that can affect young people's mental health - like academic pressure and how we support children who've lived through traumatic experiences."
Kevin Courtney, joint general secretary of the National Education Union, said that schools are being hindered by funding cuts.
"The narrowing of the curriculum, and exam factory assessment are also clearly having an impact on children and young people's mental health," he said.
"It is quite clear that government policies on education and the underfunding of public services is contributing to this destructive and distressing situation for young people and their families. The government has an opportunity at next week's Spending Review to address the shortfall of funding our vital public services desperately need."
Last week the Children's Society raised fears over children's mental health in its Good Childhood report into young people's sense of happiness.
This found that one in five children are worried about their mental health, with those living in poverty particularly concerned.
