Legal & General has published claims statistics revealing that the insurer paid out £1.9 million in children's critical illness claims in 2015.
Its figures show that the average age of child was seven, with the youngest being just one month old.
The insurer announced that 44% of the children were four years or younger, making those within that age group the most common claimants for a critical illness last year.
The fewest number of claims came from children over 15 years old, amounting to 15 per cent of the total.
Legal & General paid out for a total of 106 children's critical illness claims in 2015, the main conditions or causes being cancer, stroke, child funeral benefits, benign brain tumours and major organ transplants. Claims for cancer were by far the highest of the conditions, accounting for 60.5 per cent.
The insurer is releasing its claims statistics to raise awareness among parents that its adult critical illness policies automatically include cover for children from 30 days old up to 18 years old, or 21 years for those in full time education.
Steve Bryan, Director, Intermediary at Legal & General, said:"Child critical illness is a serious problem affecting families throughout the UK. Our data shows that there has been a year-on-year rise in claims for critical illnesses affecting children, which will make difficult reading for parents.
"While none of us like to think about our children being unwell it is crucial that parents consider reviewing their critical illness policies to work out whether their children are covered.
"To see cancer claims for children representing nearly two-thirds of those we received last year is very sad but parents who find themselves in such a situation should be reassured that there are many facilities and support mechanisms in place to help their child whenever needed."