BBC Trust chairman Sir Michael Lyons is to step down after four years in the post.
The former chief executive of Birmingham City Council has written to Culture Secretary Jeremy Hunt to explain that he will not seek reappointment next May when his term ends.
Sir Michael – the first person to take the role – said the growing workload for the part-time position had made him “increasingly concerned” that it was squeezing out other demands on his time.
The 60-year-old academic was a professor of public policy at the University of Birmingham. He is a former chief executive of three city councils – Wolverhampton, Nottingham and Birmingham. In his letter, he said the post “has been far more demanding than the nominal three to four days a week in the job specification”.
There has been some uncertainty about the future of the Trust under the coalition Government.
In his letter, Sir Michael said: “I am proud of what we have achieved in safeguarding the BBC’s independence against significant challenge, and bringing the interests of audiences in all their diversity to the centre of the BBC’s thinking.”
And Sir Michael said the Trust had “taken openness and transparency to a new level”.
He said he had made his announcement now to leave time to find a successor, and to set a “clear context” ahead of policy issue talks.