Mike Coupe will step down as CEO of Sainsbury's at the end of May after six years at the helm.

The UK's second largest supermarket group has opted for continuity by choosing retail and operations director Simon Roberts as his successor. 

Mike Coupe has faced questions about his future since April when Britain's competition regulator blocked Sainsbury's attempt to take over Walmart owned rival Asda for £7.3 billion. 

Coupe was the architect of that deal and Sainsbury's share price has fallen 22% over the last year. 

Roberts, a former managing director of health and beauty retailer Boots, joined Sainsbury's in 2017. 

Earlier this month, Reuters reported that he was the leading internal candidate to succeed Coupe. 

"Simon has been extremely effective during his three years at Sainsbury's, leading our store teams through great change in that time," said Sainsbury's chairman Martin Scicluna. 

His appointment to one of the most high profile jobs in British retail raises the question of whether he will further adapt Sainsbury's strategy that was set out in September and was designed to show the group could prosper on its own. 

Sainsbury's profit is forecast to fall in its 2019-20 year.

Roberts' task will be to grow earnings in the face of softening consumer demand and the relentless march of German-owned discounters Aldi and Lidl, who continue to aggressively open new space and win market share. 

His appointment means Britain's two biggest supermarket groups - market leader Tesco and Sainsbury's - will be run by Boots alumni. 

Irishman Ken Murphy, a former joint chief operating officer at Boots UK & Ireland, will succeed Dave Lewis as CEO of Tesco in the summer.