The Scottish Retail Consortium's latest sales monitor says food sales rose 3.5% in May Â the lowest monthly rate for more than two years Â while like-for-like sales were just 1.9% up year on year.
The off licence sector had a good month with an influx of US and Japanese tourists leading to strong sales of malt whisky. Champagne, spirits, beer and wine sold "very well".
But sales of barbecue and picnic-related items dropped because of the poor weather.
SRC director Patrick Browne said: "The World Cup and Golden Jubilee boosted consumer spending in various areas. The poorer weather in May dampened retail sales in other areas."