BP unexpectedly fired Manifold on Tuesday after eight months on the job, citing “serious concerns” related to “governance standards, oversight and conduct.” The shares dropped 4%.

People close to BP who requested anonymity said there’d been complaints about aggressive behavior by Manifold toward employees, as well as of mishandling sensitive information and seeking to bypass the board on decisions in which it should have been involved.

“I was removed without warning and without explanation,” Manifold said in an emailed statement. “I dispute entirely the characterisation of my conduct and I will not allow a false narrative to go unchallenged.”

Manifold’s dismissal is the latest in BP’s ongoing leadership turmoil, which has included three chief executive officers in as many years, and raises fresh questions about the company’s internal processes at a time when it’s seeking to turn around years of poor performance.

The oil giant has underperformed rivals in recent years after former CEO Bernard Looney, who departed after failing to disclose personal relationships with colleagues to the board, pivoted the company toward renewable energy.

“During my time as chairman I worked to drive genuine change at BP — cutting costs, challenging excess, and holding the organisation to higher standards,” Manifold wrote. “The board’s statement this morning acknowledged the focus and pace I brought.”