The number of nurses in the NHS has decreased by more than 7,000 since May 2010, according to an RCN analysis of NHS workforce statistics.
Dr Peter Carter, chief executive and general secretary of the RCN, said: "These numbers are further evidence of the damaging effect that cuts are having on the NHS. We have frequently stated our concerns that this level of cuts will have a long lasting and detrimental impact on patient care.
"The RCN recently warned the Government that the NHS was sleepwalking into a crisis by cutting nursing staff posts at a time when the nation's healthcare needs are becoming greater and more complex. The latest statistics show that the cuts to NHS staff show no sign of slowing down.
Trade union Union's own analysis of the figures reveal 8,273 health workers have left the NHS workforce since August 2011.
Christina McAnea, head of health at Unison, added: 'Patient satisfaction has declined, waiting lists are growing, wards are closing and now we know that more than 8,000 health workers have left the NHS. This will have a huge impact on patient care, which staff are vital to delivering.
"The government needs to go back to the drawing board on the NHS or risk the wrath of voters at the next election."