Calls to the service from suicidal children increased by 14 per cent last year, according to a new report. More than 1,000 youngsters contacted the charity to talk about killing themselves and 1,500 more mentioned suicide during the course of other discussions.
ChildLine is calling on the Department of Health to set up an in-depth investigation into the rising rate of suicide and attempted suicide among young people.
Esther Rantzen, the president of ChildLine, said: "All young death is agonising, but suicide is among the cruellest of all because it is preventable. One child rang ChildLine from her science lesson - she had already taken an overdose.
"Another teenage couple had made a suicide pact and rang having cut their wrists. These lives were saved, but of the 4,500 children who try to call ChildLine each day, nearly half will not get through."
The report found that girls were much more likely to contemplate suicide than boys, with five times as many female callers to the service.
According to the mental health charity Mind, 11 boys and 12 girls under the age of 14 killed themselves in 2002. But a further 373 young men and 103 young women aged 15 to 24 also committed suicide.
The suicide rate among men aged 15 to 24 is 17 per 100,000 of the population, compared with an overall rate for men of all ages of 13 per 100,000.
Experts are concerned at rising problems of bullying, self harm and other problems among children, some as young as six. The Government has pledged to stamp out bullying in schools but ChildLine says that more needs to be done.
The charity wants to see counselling facilities and peer support available at all schools. Experts estimate that up to 10 adolescent suicides a year are directly attributed to bullying and research has shown that one in 12 children are tormented to the point that it has a detrimental effect on their education, relationships and self-esteem.
Last month, Sophie Amor, 23, won £20,000 in compensation in an out-of-court settlement for the bullying she suffered at school. Ms Amor, from Wales, tried to kill herself at the age of nine and said her life was destroyed by the ordeal.
Thousands of children are also being prescribed powerful anti-depressants for mental health problems. More than one in 10 boys (11.4 per cent) and 7.6 per cent of girls aged five to 15 suffer from a psychiatric disorder. Up to 10 per cent of teenagers are thought to be suffering depression.
More than 24,000 of the 160,000 people treated in emergency departments for injuries associated with self harm each year are aged between 15 and 19, according to a recent study.
A national inquiry into rising rates of self harm among young people and the reasons behind it is due to be published in the next few weeks. Psychiatrists are concerned that units treating children with severe mental health problems are being closed because of budget cuts.