By Andy Bruce and William Schomberg
LONDON (Reuters) - British retail sales suffered their biggest slump in more than four years in December, denting what had been a promising fourth quarter and rattling sterling as more signs emerged of a pick-up in inflation since June's Brexit vote.
Consumer spending has been the main driver of Britain's economy since June's referendum decision to leave the European Union, with other sources of growth like investment and trade lagging.
Friday's data showed retail sales volumes dropped 1.9 percent month-on-month in December, far below economists' forecasts in a Reuters poll for a 0.1 percent decline and the biggest fall since April 2012.
That miss, which cut fourth quarter growth to 1.2 percent from the third quarter's near two-year high of 1.8 percent, prompted sterling to slide by almost half a cent to below $1.23.
"December's data delivered some unpleasant omens for this year," said Martin Beck, senior economic adviser to consultancy EY ITEM Club.
He pointed to annual shop price inflation hitting a three-year high of 0.9 percent, while the annual rate of sales volume growth dropped to a three-month low of 4.3 percent from 5.7 percent in November.
"The squeeze on households' real incomes is gradually tightening, implying a tough 2017 for retailers."
The Office for National Statistics' weak December figures, which can be volatile month-to-month, contrast with financial results from major retailers, which mostly enjoyed a strong Christmas season.
Policymakers have been heartened by British consumers' lack of pre-Brexit nerves, but there is also anxiety that the economy is too reliant on them for growth.
On Monday BoE Governor Mark Carney said he would keep a close eye on consumer behavior, given consumption-led expansions were generally weaker than broader-based ones, as they often became dependent on ever-higher rates of borrowing.
A Reuters poll of economists published earlier this week suggested Britain's economy is likely to grow around 1.2 percent this year - around half the rate of 2016 - although a recession is not on the cards.
The ONS said sales across all types of retailers - barring "other stores" covering among others pharmacies, bookshops and garden centers - fell in December.
(editing by John Stonestreet)