Figures from the Office for National Statistics show that the retail price index measure of inflation, which includes house prices, rose from 3.8 to 4.2 per cent.
The lower consumer price index also rose to 3 per cent, well ahead of the government target of 2 per cent.
The RCN recommended the pay deal, which gives rises of 2.75 per cent in year one, 2.4 in year two and 2.25 in year three, based on government predictions that inflation would fall.
The prospect of a fall now appears remote after Bank of England governor Mervyn King said last week that UK inflation was set to stay above government targets for at least two years.
RCN head of employment relations Josie Irwin said earlier this month that the union could ask the Pay Review Body to revise the pay deal if inflation was above 3 per cent at Christmas.
A Unison spokeswoman said it would not tell members which way to vote on the pay deal despite rising inflation.
But she admitted: ‘Members will be looking at the increases with concern.' If they accept the pay deal, the inflation clause was likely to be triggered, she said.
Lincolnshire district nurse Candice Pellett said: ‘The pay deal must match the rise in inflation.'
She said for district nurses in rural areas the high cost of petrol was a real concern, along with rising utility costs and other pressures.
‘The thinking among nurses is to accept the deal, but it must be recognised that as inflation rises, it must be looked at again.'
Members of the union Unite working in ancillary and ambulance posts this week voted to reject the deal by six to one.
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