Councillor Jenny Laing takes over from Barney Crockett as head of the ruling Labour group at Aberdeen City Council.
The move comes after several rows - including one over a school visit by First Minister Alex Salmond days before a by-election - with a growing rift between the SNP Government and the council.
Ms Laing, the city's education, culture and sport convener, is expected to take over as council leader today.
The council's SNP opposition group leader Callum McCaig said he thought the Labour group got rid of Mr Crockett as leader in an attempt to salvage its reputation.
Mr McCaig said: "They were getting a considerable amount of resistance from the general public to what people rightly perceive as an out-of-control council. "
Councillor Laing said yesterday she was "very proud" to be leader of the Labour group.
She said Mr Crockett's departure was a "democratic" process but did not give details of his exit.
She said: "We have a democratic process in the Labour group and the office bearers positions were up for re- election. We held that meeting on Monday."
Mr Crockett was unavailable for comment yesterday.