Shares in Topps Tiles fell 2.7% in Wednesday morning trading after the retailer warned that its full-year profits would come in at the lower end of market expectations.
Topps chief executive Matthew Williams said tougher market conditions had prevailed as the housing market slowed.
Topps is listed on the FTSE 250 index, which was down 0.16% at 20,004.08.
At the same time, the blue-chip FTSE 100 was down 0.05% at 7,464.57, with Tesco falling 2.6%.
The supermarket chain announced a big rise in first-half pre-tax profit to £562m as sales rose for the seventh quarter in a row.
Tesco’s shares were initially among the biggest risers on the FTSE 100 when the index opened, but as the morning progressed, it switched from being the index’s top winner to being one of the worst losers.
The retailer’s woes had a wider impact on the grocery sector, with rival Sainsbury’s also down, shedding 1.8%.
Energy firms were also hit as the government announced details of its much-heralded price cap on household gas and electricity bills.
Centrica was trading 4.9% lower, while SSE fell 2.2%.
On the currency markets, the pound rose 0.35% against the dollar to $1.3284 and edged up 0.09% against the euro to €1.1281.