Three quarters of NHS hospitals are failing to meet their own staffing targets for nurses, new data analysis suggests.
NHS England published nurse, midwife and care staffing data on the NHS Choices website in June as part of its drive for openness and transparency throughout the health service.
Health officials have said that overall 96% of organisations were meeting their own targets for staffing levels.
But the Health Service Journal (HSJ) said that these figures include both registered nurses and health care assistants - or unregulated care staff.
The magazine conducted analysis on data from 139 acute NHS Trusts to assess whether or not they had met their own targets for nursing staff levels - stripping out the data concerning health care assistants.
It found that 75%, or 105 acute trusts, were failing to meet their own targets for the number of hours worked at their hospitals by registered nurses, i n at least one hospital site.
The magazine said: " In some cases trusts falling short of nurses attempted to compensate by increasing their HCA (health care assistant) staff above planned levels, which had the effect of increasing their aggregate scores presented on NHS Choices."
The issue of safe staffing levels has become much debated in the health world since the publication of the report into the serious failings at Stafford Hospital.
The public inquiry into the scandal highlighted the "inadequate" staffing levels of nurses.
Inappropriate numbers of nurses, combined with poor leadership, recruitment and training, led to "a declining professionalism and a tolerance of poor standards", inquiry chair Robert Francis QC said.
Following the inquiry there was a call for a minimum staff-to-patient ratio to be set.
As a result of the inquiry and a patient safety review of the NHS conducted by health expert Don Berwick, the National Institute for Health and Care Excellence (Nice) was commissioned to look into safe staffing levels across NHS Trusts in England. Their final draft guidance on the s ubject is to be published tomorrow.
A Department of Health spokeswoman said: " Getting safe staffing right can't be done overnight - we're putting our full focus on it and already have 5,000 more nurses than last year."
Katherine Murphy, chief executive of the Patients Association, said: " Patients deserve the very best nursing care when they are in hospital, and this can only be delivered by fully qualified registered nurses. We have been worried for many years at what appears to be an imbalance between the utilisation of healthcare assistants in the place of registered nurses.
"We are concerned that as healthcare assistants are cheaper to recruit and pay, many hospitals are becoming more reliant upon them to bring up staff numbers on the ward. However, they lack even basic regulation and have minimal training.
"We have also heard from many patients who struggle to distinguish between different nursing roles and healthcare assistants.
"It is vital that hospital managers plan their staffing levels properly and adhere to guidelines. The director of nursing, together with the member of staff in charge of the ward or department, should review staffing levels on a daily basis and agree the staffing numbers and expertise. They should be accountable for any shortcomings."