Marc Bolland has left his post as chief executive of Morrisons two months earlier than had been expected.
Marks & Spencer's new boss was due to step down at the end of January, ahead of taking up the position of ceo at the premium retailer.
But Morrisons said he would instead "relinquish" his duties as chief executive on Friday.
A spokeswoman for Morrisons told the Press Association a start date for Bolland at M&S was "still under discussion".
The decision was made at a board meeting yesterday.
Morrisons non-executive chairman, Sir Ian Gibson, who will now chair the executive board, said: "Morrisons has a strong and capable senior management team which will continue to operate the business. We are well placed for a successful Christmas period and a strong end to our current financial year."
