Just 15 per cent of children's intensive care units across Britain and Ireland have enough staff, a report has found.
Only five out of 34 paediatric intensive care units (PICUs) met recommended nurse staffing levels, the research by the universities of Leeds and Leicester revealed.
Units will be monitored closely by the Paediatric Intensive Care Audit Network (PICANet) over the next 12 months to ensure the inadequate staffing levels do not affect quality of service, researchers said.
The report found a high percentage of agency and bank nursing staff in some regions, particularly in London, where the use of such staff was as high as 25 per cent on one night.
There was also an increase in the amount of time spent by children in PICUs, with beds being occupied for 131,268 days in 2014 - an increase of 2,748 bed days on the previous year.
Mortality rates remained low. Of 19,760 admissions in 2014, less than four per cent died after being admitted, the report found.
And there was no significant increase in the number of children admitted to PICUs over the last three years.
Dr Roger Parslow, of the School of Medicine at the University of Leeds, said: "It is gratifying to know that, despite continuing problems with staffing, we have not observed a measurable reduction in the quality of paediatric intensive care delivered by the 34 PICUs covered in the report.
"Continued pressure on the service caused by more admissions, longer stays and inadequate staffing levels may, at some stage, result in changes to the quality of service delivered. PICANet will closely monitor outcomes and processes in UK and Ireland PICUs over the next 12 months to detect any such change."
Professor Liz Draper, from the College of Medicine, Biological Sciences and Psychology at the University of Leicester, said: "Paediatric intensive care units continue to have difficulty achieving the PICS nursing standards.
"It is difficult to achieve continuity of care and the use of a designated nurse when staffing is so stretched and the complexity of care required by the children admitted to intensive care continues to rise.
"Problems with the recruitment and retention of nursing staff in this stressful environment are growing and innovative solutions are required to maintain a high-quality workforce, such as self-rostering and more flexible working for staff with families and other dependants."