Asda's retail operations director Mark Ibbotson and operations director Glenn Bowles have been touted as the favourites to replace Simon King, who left Asda earlier this week after just six months as chief operating officer.

Ibbotson, Asda's former productivity director, was in 2005 instrumental in introducing a new stock control system called Osca to improve availability. Bowles has held senior roles at the retailer, including development director, regional MD for the north and operations director for the north.

Asda would not comment on King's successor, who is expected to be announced at the end of the month, or the reasons for his exit, except to say it had been "by mutual consent".

However, a source close to the situation said: "Simon is a very capable operations man with a proven track record at Tesco, so I suspect it's either a culture clash or a personality clash with Andy Clarke and the rest of the senior team."

King's non-Asda background would not have helped, she added, and the retailer was now likely to look internally for his replacement. "Asda appears increasingly inward-focused, with Walmart clearly ready to appoint from within," she said.

King joined Asda in January following a stint as CEO of supermarket operator Panda Retail in Saudi Arabia.

Prior to that he was CEO of the Tesco-owned Kipa chain in Turkey, having also worked with the retail giant in South Korea and Eastern Europe.

At Asda, he was handed responsibility for all retail and supply chain operations.