Paul Farmer, chair of the charity leaders body Acevo, has stepped down from the role for personal reasons.
The chief executive of the mental health charity Mind was due to relinquish his Acevo position in December after four years, but has stepped down with immediate effect to devote time to supporting his wife through a serious illness.
Farmer has been at Mind since 2006 and was voted Most Admired Chief Executive by readers of Third Sector in 2013.
A spokeswoman for Mind said his position at the charity remained unchanged.
Joe Irvin, vice chair of Acevo and chief executive of Living Streets, which campaigns on behalf of pedestrians, has become chair of Acevo until the umbrella body’s annual general meeting in December, when he will have reached the maximum six-year term and must step down.
Acevo has launched a recruitment exercise to find a new chair to take up the role for the next three years, with the possibility of a second three-year term.
Irvin, a former chief executive of the local infrastructure body Navca, will lead the recruitment process.
Vicky Browning, chief executive of Acevo, said: "I would like to thank Paul Farmer for the unwavering support, calm approach and skilled leadership he has shown during his time as chair."
She said the charity was looking for a leader who could lead its board with "an enabling and inclusive approach in order to bring out the best of board members and the executive team".
"We’d like to talk to candidates that have a depth of experience, but a lightness of touch," said Browning.
Applicants must be full or associate Acevo members.