Figures for July showed Consumer Price Index inflation rose 0.6% to 4.4% – the largest increase since records began.
This means that the three-year pay deal for nurses, worth just under 8% until 2011, is unlikely to keep pace with inflation.
The government has stated that it wishes to limit public sector pay rises to 2% over the next three years.
Unions are already investigating triggering a reopener clause in the deal, which gives the NHS Pay Review Body an opportunity to recommend improvements to the deal should inflation increase.
Dave Prentis, Unison general secretary, said: ‘This rise just confirms what our members have been telling us for months - they are facing unparalleled hikes in the cost of basics like milk, bread, cheese, petrol, gas and electricity.
'The government¹s unjust public sector pay policy means that teaching assistants, nurses, librarians, care workers, home carers, nursery staff and hospital cleaners are having to cope with the biggest rise in inflation since records began, on a real pay cut.
'Instead of targeting the public sector workers who keep this country running, the government should turn their firepower onto the big city bonuses and corporate fat cats who are the real villains when it comes to fueling inflation.'