Sales have fallen at DIY store chain B&Q and trade tools seller Screwfix due to "challenging" trading conditions.
Parent Kingfisher said like-for-like sales across the two businesses fell 5.5% in the 11 weeks to 16 July.
Kingfisher said B&Q was also affected by rival Focus DIY going into administration, which resulted in Focus cutting prices to clear stocks.
Ian Cheshire, Kingfisher's chief executive, said: "These are testing times for retailers."
Sales at Kingfisher's two French chains, Castorama and Brico Depot were much stronger, adding 3.7% on a same-store basis during the 11 weeks.
Across Kingfisher's outlets in Poland, China, Spain and Russia, like-for-like sales added 1.4%. More...