Sainsbury's new chairman Martin Scicluna will take up his role on Sunday, the company said on Friday, in the midst of its battle to salvage a $9.5 billion (€8.47 billion) takeover of rival Asda and hold on to its position as Britain's number two supermarket group.
The company said current non-executive chairman David Tyler would step down on 9 March and be succeeded by Scicluna, who holds the same role at insurer RSA, the next day.
It said last July that Scicluna would take over from Tyler, who has been chairman for the past nine and a half years, but did not give a precise date.
Scicluna starts the job at a difficult time, after Britain's competition regulator said last month its initial view was that Sainsbury's purchase of Walmart's Asda should be blocked in the absence of the sale of a large number of stores, or even one of the brands.
The regulator will publish a final ruling by 30 April Sainsbury's chief executive, Mike Coupe, seen as the architect of the deal, could come under investor pressure if it fails.
Industry data published this week also showed Sainsbury's continuing to underperform rivals, including market leader Tesco and number four Morrisons.
At current run rates, Sainsbury's could lose its number two status to Asda when the next data set is published on 30 April.