More than 60 NHS hospital trusts have been asked to cut their pay bill after recruiting extra nurses in the wake of the Mid Staffs scandal.
Patients groups have reacted with fury, warning that pressure to cut staff numbers could jeopardise patient safety.
Earlier this month the Health Secretary said there must be "no compromise" on safe staffing, having warned against "scrimping" on nurse numbers.
In the wake of the scandal, he paid tribute to hospitals for taking on thousands more nurses to improve patient safety.
However, NHS regulators have now told 63 NHS trusts that they appear to be spending too much on staff.
The body, called NHS Improvement, has singled out organisations whose pay bill has grown by more than inflation, with