Asda chief executive Sean Clarke will stand down in January, barely 18 months after taking on the role.
The supermarket chain, a subsidiary of US giant Walmart, has struggled over the past few years, losing market share to discount rivals Aldi and Lidl.
But it insisted Mr Clarke was departing because he wanted to take some time out, and that his deputy Roger Burnley was always being lined up as a successor.
Dave Cheesewright, chief executive of Walmart International, said: “Roger was purposefully brought back to Asda to partner with Sean ahead of the transition to Roger taking up the position of CEO.
Mr Clarke joined Asda from Walmart’s Chinese division last year
“He and Sean have worked as a great team and I’m really confident in Roger’s ability to continue building on our return to momentum.”
Mr Clarke has spent 21 years in various international roles at Walmart and was chief executive of its Chinese division before taking the top job at Asda last July. He replaced Andy Clarke, who had struggled to maintain the retailer’s revenues amid intense competition and falling food prices.
He is expected to return to another role at Walmart after taking some time out, an Asda spokesman said.
Clive Black, an analyst at Shore Capital, told The Daily Telegraph it was a “surprise” Mr Clarke was leaving given his relatively short tenure. However, he added: “Roger Burnley is a very experienced UK grocer, something that Sean has lacked.”
Mr Burnley was previously director of supply at Asda but left to become Matalan’s supply chain director in 2002. He later held the same role at Sainsbury’s before returning to Asda as deputy chief executive and chief operations officer in October 2016.
Mr Black said: “To take Asda forward they do need an experienced British supermarket general. Roger Burnley is up against [Tesco chief executive] Dave Lewis, [Morrison’s] David Potts and [Sainsbury’s] Mike Coupe in the larger store segment and they’ve been around a long time.”