Retailers lifted their prices by an annual 0.3 percent, the biggest increase since April 2013, the British Retail Consortium and market research firm Nielsen said.
In November, prices rose by 0.1 percent.
Retailers have held down their prices in the face of tough online competition and weaker household spending power.
December's increase represented only the fourth month of inflation in shop prices in five years, the BRC said.
Food price inflation eased to an annual rate of 1.5 percent from 1.6 percent in November. But non-food prices showed the smallest decline since March 2013, falling by 0.4 percent.
The easing of fresh food price increases was likely to be a first sign of downward pressures from lower international food prices which began to fall in mid-2018, the BRC said.
However, consumers could end up paying more if Britain fails to leave the European Union smoothly, the BRC warned.
"Without a trade deal with the EU, the cost of importing many of the goods we buy day-to-day will go up significantly and retailers simply do not have the room in their margins to protect consumers," BRC chief executive Helen Dickinson said.
Prime Minister Theresa May is struggling to overcome deep opposition in her Conservative Party and among other lawmakers to her Brexit plan, raising concerns about an abrupt, no-deal Brexit in less than three months' time.
Britain's official measure of consumer price inflation stood at 2.3 percent in November, down from a peak of 3.1 percent a year earlier but still higher than the Bank of England's 2 percent target.
The BoE expects inflation to drift down as it raises interest rates gradually.
(Reporting by William Schomberg; editing by David Milliken)
