The Office for National Statistics (ONS) said retail sales volumes rose by 1.3% from a revised 1.8% in April.
Economists polled by Reuters expected sales to rise by 0.5%.
The latest numbers will be a relief to retailers who have had a torrid time of late and may give the Bank of England opportunity to raise interest rates. Sterling rose almost half a cent against the dollar to $1.3430.
"Retailers suggested that a sustained period of good weather and Royal Wedding celebrations encouraged spending in food and household goods stores in May," the ONS said.
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Many high street retailers have been forced to axe staff and close stores as consumers become more cost conscious and more shop online. House of Fraser became one of the biggest casualties. It plans to close more than half its stores, including its flagship Oxford Street outlet, with 6,000 jobs on the line.
And the latest victim, N Brown, which owns the JD Williams, Simply Be and Jacamo retailers plans to close 20 stores, putting 270 jobs in doubt. It blamed weak footfall on the high street for the move.