The Government has been accused of "hiving off" parts of the NHS after announcing privatisation plans for an agency which provides thousands of nurses and other health workers to hospitals across the country.
The Department of Health said it planned to explore options with the private sector for potential investment in NHS Professionals, which has 50,000 workers on its books.
It provides staff to cover more than two million shifts a year and recruits around 1,000 workers every month, working with 77 acute, mental health, foundation and primary care trusts.
NHS Professionals, a limited company owned by the Health Department, provides a range of services including nursing, medical, admin and clerical staff to NHS Trusts across England.
Karen Jennings, head of health at Unison, said: "The whole reason that NHS Professionals was set up, was because private agencies were ripping-off hospitals by charging them outrageous fees for recruiting or finding staff for shifts. It makes no sense at all to bring back private companies who will want their slice of the action in return.
"This proposal is purely about Tory plans to promote privatisation and hive off parts of the NHS to private companies, regardless of the consequences on patient care.
"At a time when hospitals are being forced to make huge savings, pushing up staffing costs unnecessarily is very damaging. A sell-off may bring a short-term cash injection, but cost NHS Trusts vast sums in the longer term."
