Health services for children with diabetes in the South East are failing to receive high enough priority, according to a survey by Diabetes UK.
The government says progress has been made
The charity said three quarters of primary care trusts in Kent and Sussex do not have a suitable system for treating diabetic children.
It also says fewer than half have a strategy to identify diabetes early.
The report, called Your Local Care 2004, accepted that some improvements had been made in treating patients.
However, the study by independent research company Dr Foster found that services varied from region to region.
In the South East, only 33% of PCTs had written protocols for the initial treatment and assessment of children compared with 60% nationally.
Meanwhile, 33% had plans for transferring children to adult care, compared with 52% nationally.
"The government's policy of putting decision making in the hands of PCTs is allowing gaps to open," said Douglas Smallwood, chief executive of Diabetes UK.
Health minister Rosie Winterton said considerable progress had been made in services for diabetics.
"We recognise that in some areas there is more work to do so they can reach the levels of the best," she said.
About 1.8m people in the UK have been diagnosed with diabetes while 1m more are thought to have the condition but are not aware of it.
Some types of diabetes are treated with the hormone insulin while others are controlled with diet and drugs.
Long-term complications include blindness, kidney failure and heart attacks.