LONDON (AFP) ― Britain’s biggest retailer Tesco said Monday that chief executive Philip Clarke will step down in October, as the troubled supermarket giant warned that first-half sales and profits would miss expectations.

Clarke, who has been at the helm for three years, will be replaced by Unilever executive and turnaround specialist Dave Lewis, Tesco said in a statement, as the group struggles with what it described as “challenging” trade.

“Tesco plc announces that Dave Lewis will join the board of Tesco on Oct. 1 as chief executive officer in succession to Philip Clarke,” the company said.