According to the study, entitled Our NHS - Today and Tomorrow, some 22,300 health jobs have been lost across various trusts as a result of redundancies, freezes on recruitment and post closures.
In addition, almost three-quarters of newly-qualified nurses have been unable to secure jobs, the RCN warned.
The government has rejected the union's figures, describing them as being "outdated and misleading".
But nursing leaders insist that a financial crisis in the NHS is impacting upon patients, particularly in regard to those needing specialist care for conditions such as diabetes and heart disease.
A poll of 807 specialist nurses completed by the RCN as part of its report found that one in five were at risk of being made redundant.
Of those questioned, 87 per cent said they thought that NHS cuts were having an adverse effect on patient care, with 47 per cent aware of cuts that had been made to services in their specialist area.
Defending the RCN's figures, the union's general secretary Dr Peter Carter stressed that while the NHS achieved an overall financial balance last year, deficits were continuing to compromise patient care, services and jobs, with many local health trusts still facing cash shortages.
"This is hitting services, hurting patients, undermining staff morale and threatening the hard-won progress made over recent years," he warned.
Dismissing the RCN's claims, health minister Andy Burnham said that the union's report presented "an outdated and misleading picture".
"We recognise it has been tough for NHS staff over the last 12 months, but we have now put the NHS on a sound financial footing for the future," he insisted, with the government claiming that the RCN figures on job losses related to a "natural turnover of staff".
However, opposition parties seized on the report as evidence of the government's "financial mismanagement" of the health service.
"It is a damning indictment of the cost of Gordon Brown's NHS cuts and Patricia Hewitt's poor stewardship," said shadow health secretary Andrew Lansley in an attack on the policies of the chancellor and his government counterpart.
Liberal Democrat health spokesman Norman Lamb said the RCN's report was "devastating" for the NHS.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.