The YouGov survey of 1,600 young people aged 11 to 24 found that 33 per cent admitted to not feeling confident.
However, when broken down by age, 73 per cent of the 11-year-olds in the study said they did feel confident. By contrast, only 45 per cent of 17-year-olds reported that they felt confident.
The results also show a gender divide, with girls more likely to feel unconfident than boys.
When asked what it was that affected their confidence, the young people blamed exam pressures, relationships, and defining their identity. For girls, appearance and the clothes they wear were the biggest factors in feeling unconfident.
The research also found that two in five of the respondents aged 14 to 17 said that they feel they can be more confident on social media channels than in person.
Meanwhile, a survey of 600 parents carried out alongside the student research found that mums and dads tend to have an overinflated sense of their children’s confidence levels.
Parents also underestimate the impact that certain situations might have on their children.
The study confirmed that both parents and the young people believe confidence is an important factor to being successful.
Also important, they said, were attributes such as communication skills (98 per cent parents, 95 per cent young people), confidence (97 and 90 per cent), and resilience (96 and 91 per cent).
These aspects were all rated as more important than “being clever”.
Commenting on the findings, child confidence expert Annette Du Bois said: “Today more than ever before, young people across the UK are feeling emotional imbalance, general insecurity, low self-esteem and a lack of confidence, creating anxiety and mild to excessive unhappiness.
“The modern and complex world has created the fertile ground upon which emotional and psychological pressures are felt much earlier on.
“Trying to keep up, gain acceptance or fit in, both online and offline, can lead to a decline in wellbeing, life-skills, and social interaction.”
The survey was commissioned by Sky Academy – a series of initiatives aimed at encouraging young people’s potential. Commenting on the research, Lucy Carver from Sky Academy said: “It’s clear that confidence plays a crucial role in helping young people succeed and unlock their potential.”