Speaking at a press conference on Wednesday, Tamim said the move is part of the board's plan to return to a two-captain system, with separate leaders for red-ball and white-ball cricket.
"We had three captains across the three formats. I believe we should have two captains, and the board shares the same view," Tamim said.
Explaining why Litton was chosen to lead the ODI side instead of retaining Miraz, the BCB president praised the all-rounder's leadership but stressed that his performances as a player remain the priority.
"Miraz is a successful captain. He won four out of five series. But I believe we need Miraz more as a cricketer. We are used to seeing him perform at a certain level, and perhaps there has been a slight drop. While he has batted well, there is still room for improvement with his bowling."
Tamim added that he had spoken with Miraz before the decision and that the all-rounder understood the board's thinking.
"I've spoken to him and he understands the situation. We believe in a two-captain system so both leaders can plan and prepare properly."
Under the new structure, Najmul Hossain Shanto will continue as Bangladesh's Test captain, while Litton will lead the side in the white-ball formats.
Towhid Hridoy has been appointed vice-captain across both ODI and T20I cricket.
The decision ends Miraz's stint as ODI skipper and marks another leadership change ahead of Bangladesh's busy international schedule, including the 2027 ODI World Cup cycle.
