John Hilary, executive director of the anti-poverty charity War on Want, is to step down after 12 years at the organisation.
Hilary, who joined War on Want in 2004 as director of campaigns and policy before becoming executive director in 2008, said in a statement yesterday that he would leave in October.
A spokesman for War on Want said Hilary, who is 51, planned to take some time out before deciding on his next move.
The statement from the charity said Hilary had led War on Want through a period in which it had grown its income to new levels, expanded its staff team and launched new programmes with grass-roots social movements around the world.
Hilary said it had been an "honour and a privilege" to have led the organisation.
"The values and principles that War on Want upholds have never been more important than they are today, and I have no doubt that it will continue to make a real difference in the struggle for social justice across the world," he said.
"I look forward to supporting War on Want in new ways over the coming years, as well as joining in its campaigns as an ordinary member. I will always be proud to have worked for such an inspiring cause."
Steve Preston, chair of War on Want, said Hilary would be greatly missed. "His leadership and energy have been an inspiration, and it has been a great pleasure for me personally to work closely with him as chair," said Preston.
"War on Want continues to go from strength to strength, and we are truly grateful to John for playing such a major part in that success."