Marks & Spencer Chief Finance Officer Alan Stewart will leave to join Tesco in the same role.
Two days after helping M&S Chief Executive Marc Bolland present first-quarter sales, Mr Stewart has left Britain's biggest clothing retailer to join the world's third-biggest stores group on an increased salary of £1.7m.
His appointment will be a boost to Tesco CEO Philip Clarke, who is currently the only executive on Tesco's board, and who is facing questions over whether he has the right strategy to turn around the group.
"We wanted a candidate who had the right blend of experience, leadership and values to play a leading role in the transformation of Tesco. We have found all three in Alan," Mr Clarke said.
Mr Stewart abruptly left the M&S central London headquarters after handing in his notice yesterday, a source familiar with the situation said. But he is unlikely to start work at Tesco before the end of this year due to a six-month notice period and the triggering of a non-compete clause in his contract, the source said.
Shares in M&S were down 1% at midday, while Tesco's shares were up 0.5%. Tesco's shares are hovering near 10-year lows, while shares in M&S are down over 40% since their peak in 2007.
Tesco, which has been looking for a new finance chief since Laurie McIlwee announced his intention to resign in April, said Mr Stewart would join "following satisfaction of existing contractual obligations."
Mr Stewart has held the CFO role at M&S since October 2010 and had responsibility for property added to his role just 11 days ago when Mr Bolland shuffled the remits of his executive team.
Mr Stewart is a former finance director of WH Smith and has also held executive roles at HSBC and Thomas Cook.