The number of children admitted to English hospitals as emergencies has increased every year since 2003, researchers have found.
The largest rise was seen among children aged under five, according to a study published in the journal Archives of Disease in Childhood.
Common infections accounted for much of the increase, which the authors suggest indicates a "systemic failure in the NHS" to assess children with acute illness that could be better managed by GPs, out of hours services or the NHS Direct telephone helpline.
The study examined hospital admission rates for under-15s and national population estimates from 1999 to 2010. During this period emergency admissions rose by 28% from 63 per 1000 of the population in 1999 to 81 per 1000 in 2010.
The proportion of children under 12 months being taken to hospital rose by 52%, while the figure for one to four-year-olds increased by 25%.
Emergency admissions for children aged under five has risen by around 3% annually, and in 2010 accounted for almost two-thirds (68%) of all such admissions.
The report, led by Peter Gill of Oxford University's Radcliffe Observatory Quarter, blamed the figures on changes to family doctors' contracts in 2004 which allowed them to opt out of providing out of hours care.
"The increasing admission of children for very short term care, particularly for acute infections, certainly suggests a reluctance of primary care to observe and manage sick children with self-limiting infections in the community," the study concluded.
It also suggested that lower referral thresholds, increasingly anxious parents and a reluctance among doctors to accept risk may also have contributed to the rise.