Government figures show that nurse numbers could be cut by more than 13,000 over the next five years, the Conservatives have claimed.
If similar losses occur over the next four years the total workforce will fall from 329,372 in 2008 to 315,963 by 2014, they said.
Shadow health secretary Andrew Lansley told the Daily Mail he was concerned that manager recruitment was outstripping that of nurses.
“Conservatives are committed to recruiting additional health visitors and to ensuring that efficiency savings in the NHS and cuts in bureaucracy are invested back into frontline services,” he said.
The Royal College of Nursing said the government needed to address the issue as a matter of urgency.
RCN chief executive and general secretary Peter Carter said: “As well as keeping trained and experienced staff in the profession, and making it easier for those who have left to return, we must make sure that nursing is an attractive profession.
“This means that people who do choose to study to become a nurse must get the financial and educational support they need to pursue their studies and their careers.”
He added: “The RCN has been saying for some time that with up to 200,000 nurses due to retire in the next decade, there is a serious crisis looming which any government must address as a matter of urgency.”