The amount spent on clothing and footwear fell by 6.4% year on year in March, according to the Office for National Statistics.
The volume of items bought in these categories was down 6.2%.
Overall, the amount spent across all sectors of retail, including food and household goods, fell 0.1%. The volume of goods bought was up 2.7% - below the 4.4% analysts had expected.
The value of online sales increased by 8.9% year on year in March.
Ian Geddes, head of retail at Deloitte, said: “Evidently, the early Easter weekend did not live up to analysts’ expectations for boosting March’s sales. Retail sales values fell in food, clothing and footwear segments, which is particularly unexpected considering the time of the year.
“We have reached a new milestone in online and digital sales, which have grown 8.9% compared to March 2015. One reason for this is simply down to the increase in smartphone and tablet ownership: 76% of UK consumers have access to a smartphone, and 60% to a tablet.
“The boost in online sales is an indication that retailers’ digital investment is starting to pay off.
“The retail industry will have to remain adaptable to changing consumer confidence and spending patterns in the short term, particularly given economic and political uncertainty in the coming months.”
Keith Richardson, managing director for the retail sector at Lloyds Bank Commercial Banking, said: “Not even the combination of an early Easter and Mother’s Day could shelter retailers from Storm Katie and the headwinds of slowing consumer spending, resulting in a second successive month of falling sales.
“The four-day Easter weekend normally brings with it bumper sales of food, spring fashion and plenty of DIY and gardening goods as families use the extra days off to spruce up their homes.
“[But] Easter came too early for people looking to refresh their spring wardrobes.
“Retailers will now be hoping that those workers who receive a pay rise in April, thanks to the new national living wage, choose to spend it on the high street, instead of on leisure and entertainment, which have to date been the primary beneficiaries from increases in consumer spending power.”