Almost one in every seven British children starting their secondary school careers feels lonely "often", new figures show.
The Office for National Statistics (ONS) states that 14 per cent of children aged 10-12 say they often feel lonely. The total reduces to 8.6 per cent for those aged 13-15, the figures show.
Conversations with youngsters also revealed that transitions linked to schooling can trigger loneliness.
The report marks the first time that the statistics body has analysed children and young people's views and experiences of loneliness.
The data, drawn from various surveys of children and young people, also shows that youngsters living in cities are more likely to report often feeling lonely compared with those who live in the countryside or towns. Among those aged 10-15, 19.5 per cent of children living in a city report "often" feeling lonely compared with just over 5 per cent of those living in either towns or rural areas.
Children in this age bracket are also more likely to report feeling lonely if they are receiving free school meals, have health problems or have poor relationships with friends and family.
The data also includes figures from young people aged 16-24 from across England, which show that one in 10 (9.8 per cent) report feeling lonely "often".
The ONS says children and young people are embarrassed to admit to loneliness, seeing it as a possible "failing".
Youngsters made a series of suggestions on what could be done to help, including making it more acceptable to discuss loneliness at school; preparing young people better to understand and address loneliness in themselves and others; and encouraging positive uses of social media.
ONS statistician Dawn Snape said: "This is our first ever report on children's loneliness – part of work we are doing to provide insight into this important social issue that can impact on people's health and wellbeing.
"We've looked at how often children and young people feel lonely and why. An important factor is going through transitional life stages, such as the move from primary to secondary school and, later, leaving school or higher education and adapting to early adult life.
"This work supports the government's loneliness strategy, announced by the prime minister in October."
Commenting on the figures, Eleanor Hevey, senior policy and advocacy manager at the British Red Cross, said: "We know that key life transitions or events, such as bereavement or experiencing bullying, can contribute to feelings of being alone.
"These findings from the ONS underline the importance of educating children and young people about loneliness and the impact it can have on a person's wellbeing.
"We fully support efforts to emphasise the importance of being connected, socialising and maintaining friendships, as part of primary and secondary curriculums."