Marks & Spencer chief executive Sir Stuart Rose will leave the retailer next March, earlier than he was obliged to.
Headhunters have been appointed to find a new chairman, M&S said.
M&S deputy chairman Sir David Michels said: “The board has set out this process to ensure a smooth transition over the coming months and enable Marc to draw on Stuart’s considerable expertise.
“We are pleased to be moving into the final stage of our commitment to split the roles and appoint an independent chairman by March 2011.”
Rose’s elevation to the role of executive chairman in 2008 prompted a run-in with investors, who complained that the arrangement did not meet best corporate governance practice.
Rose had hinted, most recently at the Retail Week Conference a fortnight ago, that he would probably not stay at M&S until the end of July 2011 - the last possible date for a transfer of power.
Rose joined M&S as chief executive in 2004 to defend the retailer against a bid from Arcadia tycoon Sir Philip Green. Under his leadership M&S once again delivered profits of £1bn, but sceptics continued to argue that he had not presided over sufficiently radical change.
As chairman, Rose’s salary will be £875,000.