Maciver's departure was revealed alongside four senior management appointments at the supermarket, where strong growth has recently slowed.
Richard Lancaster has been promoted to marketing director, to "bring together the marketing and customer services strategies to strengthen further the Morrisons brand".
He was trading director for ambient categories, having previously been managing director of Netto.
Morrisons has also made a significant hiring to lead the development of its own-label brand, appointing Belinda Youngs, chief marketing officer at Sobeys, a national grocery chain in Canada, to the own-brand director role.
Lancaster and Youngs will report to Richard Hodgson, the group commercial director who joined from Waitrose in June last year.
Another newcomer reporting to Hodgson is Nick Collard, who has left his brands director role at Boots to take the role of commercial director, ambient & frozen.
The third hiring is Gordon Mowat as strategy director, reporting to chief financial officer Richard Pennycook. Mowat joins from McKinsey, where he was one of the leaders of the European consumer goods and retail practice.