It found that most staff lacked urgency and failed to appreciate the seriousness of some severe injuries.
The independent body's report, "Trauma: Who Cares?", found that because most centres only dealt with just one case a week, skills were not up-to-date.
The NCEPOD seeks to assist in maintaining and improving standards of medical and surgical care for the benefit of the public by reviewing the management of patients, by undertaking confidential surveys and research.
Every year between 3,000 and 4,000 severely injured people are admitted to hospital.
Wrong decisions were often made and the level of care for patients was poorer at night, despite that being the time when most trauma cases are reported.
Trusts around the country should make trauma teams available around the clock, the report said.
The report was based on the care of 795 emergency patients - 344 of whom got "good" treatment - from 200 hospitals in England, Wales and Northern Ireland.
The report's authors, many of whom are leading surgeons, said the findings were "concerning."
"The current structure of pre-hospital management is insufficient to meet the needs of the severely injured patient," concluded the report, one of the largest of its kind.
"The organisation of pre-hospital care, the trauma team response, seniority of staff involvement and immediate in-hospital care was found to be deficient in many cases."
It called for urgent and major improvements to be made to prevent unnecessary deaths in the future.
NCEPOD clinical co-ordinator, Dr George Findlay, the report's co-author, said health officials "need to look at how we can organise trauma care on a regional basis". His colleague and co-author, Simon Carter, said "significant improvements" were needed "in order to prevent the unnecessary death of young patients with its tragic consequences for families".
The health minister, Ben Bradshaw, welcomed the report.
The government has previously advocated establishing specialist trauma centres which campaigners claimed would see almost 30 hospitals closed.