B&M suffered a 1.6% fall in like-for-like revenues in its third quarter.
The fall in sales in the period to December 29 compared to 3.9% growth for the same period in 2017.
Group revenues increased by 12.1% for the quarter to just over £1bn, but that level of growth was down on the 22.9% achieved in the previous comparable period.
B&M said it had a “pleasing finish to the quarter” after a “difficult November”. In December, B&M’s UK like-for-like sales rose 1.2%.
It also said “positive trading momentum” has carried into January and careful inventory control would “provide further support to the margin” over the fourth quarter.
The value retailer opened a net 20 new stores in the quarter.
Chief executive Simon Arora said: “Despite the broader economic uncertainty over the last quarter, B&M is on track to deliver a record year for both sales and earnings, representing our 14th consecutive year of profit growth.
“The business’ ability to manage profitability through uncertain trading conditions is testament to the resilience of the business model and the strong operational controls we have in place. We continue to open new stores and win market share when other retailers are retrenching.”