The managing director of Lothian Buses, Richard Hall, has announced he will step down from his role at the publicly-owned bus firm.
The decision comes just days before councillors were due to discuss how they could have greater scrutiny over the company.
Mr Hall joined in April 2016 and oversaw Lothian's expansion into new routes to the east and west of Edinburgh, with the company picking up the Scottish Public Transport Operator of the Year award in 2018.
However claims of a "toxic culture" of bullying at the firm meant hundreds of bus drivers voted to strike at the busiest time of the year. The industrial action was later called off.
The company's "huge" new buses were also criticised over a lack of space for buggies and wheelchairs.
At Thursday's meeting of Edinburgh council's transport committee, a motion from cllr Kevin Lang would have required Mr Hall to answer the committee's questions annually.
Cllr Lang said he had no reason to believe the resignation was in response to his motion.
However another councillor says Lothian Buses must become more publicly accountable and passengers should have a greater say.
Mr Hall, Lothian's Managing Director said: "Lothian has been a huge part of my life over the last 4 years.
"Our business never sleeps, we deliver for customers 24/7, 365 days of the year and that operational intensity of running public transport is extremely high and the time has now come for me to take on a new challenge.
"It has been a tremendous privilege to serve as Lothian’s Managing Director and I am incredibly proud of all that we have achieved as a team. I would like to thank all the people that I have worked with at Lothian for their commitment, assistance and support over the years."
He will step down from his position after the next board meeting on March 5, with Nigel Serafini taking over as interim managing director.
Cllr Scott Arthur tweeted: "I'm sad he stood down rather than fix the accessibility problems he introduced. His resignation, however, offers an opportunity to review how Lothian Buses are managed.
"A publicly owned company must be publicly accountable - cllrs & passengers must have a greater say."
Jim McFarlane Lothian's Chair added: "On behalf of the Board I would like to thank Richard for the significant contribution he has made across Lothian during his time as managing director.
"Under his leadership Lothian has seen significant geographic expansion of the business in addition to growth in customer numbers, revenues and profit.
"We would like to take this opportunity to wish Richard all the very best in his future endeavours."
