The union's move for an enhanced pay deal comes in the wake of increases in the costs of fuel, energy and food which are driving inflation well beyond the 2% increase predicted when the deal was struck two months ago.
UNISON head of health Karen Jennings said: "Nurses and other health workers are already struggling to cope with almost daily increases in the cost of basic necessities such a food and energy.
"The reopener clause was central to this year's multi-year pay talks because it provided a much-needed safety net against just this situation."
Ms Jennings said that 2.54% and 2.5% increases negotiated for the next two years were "well short" of anticipated inflation figures during the period.
UNISON and other health unions are to submit new evidence to the NHS pay review body arguing for a review of 2009-2010 pay rates.
This week, Local Government Chronicle (LGCplus article) reported that talks between Unison and Unite over this year’s disputed deal for local government workers could be resolved with a three-year settlement.
LGC's Jim Dunton told LGCplus: "Negotiators representing local government staff at pay talks starting on August 13 could well feel this move will adds weight to their case for a better settlement than the 2.45% offered this year.
"Health colleagues demanding a return to the table over a deal that is essentially better than the offer to council workers in each of the three stipulated years has to be a positive argument for them."