NHS Direct is to close most of its call centres with the loss of hundreds of nursing and other jobs, union leaders said.
Unison said 24 out of 30 sites will close at the service, which employs 1,500 frontline nursing and other professional staff.
Sandra Maxwell, Unison's convenor at NHS Direct, said: "Hundreds of dedicated nursing and NHS professionals are to be made redundant at a huge cost, when their skills could be used within the new NHS111 service if only the Department of Health took some decisive action."
National officer Michael Walker said: "The Secretary of State for Health should step in and stop this disaster immediately. We need action and we need it now.
"Axing dedicated hard-working nurses is never a good idea at any time, but this will directly impact on patient care. There is no doubt that patients will suffer as a result of this move."
Unison said large centres in Bristol, Sheffield, Wakefield, Nottingham, Hull, Stafford, Chelmsford and Newcastle were among those set to close.
"Given that many of these NHS call centres are in areas of high unemployment there are very real fears for the staff's future job prospects.
"The Government spending millions on making nurses and NHS professionals redundant at a time when the NHS is under great strain is truly scandalous," said a union spokesman.