The Safe Staffing Alliance (SSA) says wards often have just one registered nurse looking after eight patients.
The SSA says research shows when nurses are asked to look after more than eight patients there is an increased in risk of harm or death.
The warning comes as a poll for the Sunday Mirror and the Nursing Standard journal found that more than three quarters of nurses believe a scandal similar to that in Mid-Staffordshire could happen again.
In the poll of 2,000 nurses, 40% said on their last shift there were not enough staff to provide a safe level of care.
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A band of persistent, occasionally heavy rain moves eastwards over the region.
Winds increasing further on Monday morning with a persistent band of rain sinking south across the area by midday.
Thousands of runners took part in the Great Birmingham 10K. The 6.2mile event went around the city, ending on Broad Street.