The rainbow coalition running Dumfries and Galloway Council has been reshuffled after just eight months.
Labour and SNP co-leaders were appointed – with independent and Lib Dem support – after elections in May.
However, Labour has left the leadership due to what it said were “clear political and policy differences”.
It has pledged to keep working with other groups but the Conservative opposition said it was a “chaotic alliance” still “clinging on to power”.
The coalition was formed in the name of “mutual trust and understanding” to “work jointly on what really matters” to people across the region.
The SNP’s Stephen Thompson and Labour’s Linda Dorward were appointed co-leaders but she has now quit that role with her party colleague Archie Dryburgh moving into a role of civic head.
Lib Dem Richard Brodie, who leads the independent group, becomes depute leader.
Mr Thompson said the new arrangement would “more accurately reflect the roles” of the parties involved in running the council.
Ms Dorward said that despite stepping back from leadership, Labour would still work with other parties on common policy issues.
No political group has enough seats on the 43-member authority for outright control.
The Conservatives have most councillors with 17, followed by the SNP’s 11, eight for Labour, five independents, one Lib Dem and one non-aligned.
Conservative group leader Gail Macgregor called the latest changes “little more than deck chair moving” which “ignored the democratic will” of people in the region.
She added that she would now formally withdraw from participation in future leadership and budget panels on the council.