LONDON (Reuters) - Confidence among British consumers fell sharply in the days after the country decided to leave the European Union, according to a survey published on Thursday which gave a first glimpse of how the shock referendum result has affected households.

The YouGov/CEBR Consumer Confidence Index, which measures people's economic sentiment on a daily basis, slumped to its lowest level since May 2013, when Britain's economy was just starting to emerge from its post-financial crisis sluggishness.

Scott Corfe, a director at the Centre for Economics and Business Research, said households were "highly spooked" by the referendum outcome which would hurt retail sales and household spending, particularly on big-ticket items.

"A recession certainly cannot be ruled out at this point," Corfe said in a statement.

Britain's consumers have been the main drivers of the country's economy which outpaced most of other rich countries in past three years but showed signs of slowing ahead of the referendum which resulted a surprise decision to leave the EU.

Bank of England Governor Mark Carney, who before the June 23 vote raised the possibility of a recession if voters chose to leave the bloc, is due to give a speech at 1500 GMT (11:00 a.m. EDT) on Thursday.

YouGov said the index fell to 104.3 between June 23-27 the vote from 111.9 in the first three weeks of June.

(Writing by William Schomberg)