The former Archbishop of Canterbury Dr Rowan Williams is to take up a new social justice role next month as chair of Christian Aid's Board of Trustees.
Dr Williams stepped down as Archbishop of Canterbury at the end of last year to become Master of Magdalene College, Cambridge.
He said he had become more aware of the priority of development and aid issues around the world during his 10 years as Archbishop.
Dr Williams takes up his position as Christian Aid chair on 1 May in time for the start of this year's Christian Aid Week, which kicks off on 12 May.
He said he was "delighted" to be a part of the development agency's work.
"I believe it's of the first importance that Christians say we live from a set of values, the Kingdom of God, that will challenge a great deal about the way the world runs," he said.
"While we're not in the business of violent revolution, or the expectation of overnight change we have to go on saying change is possible, we've seen it happen, we can make it happen and with the grace of God we go on with a commitment to making it happen.
"Christian Aid has a major role to play in this with its fight against the systems and structures that force people to live in poverty. It is essential that the organisation retains its radical agenda for bringing about change.
"We are in Christian Aid because we're not prepared to sit down quietly under a system that seems unjust, that seems radically to push people out of the way for the sake of profit."