'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,' said Dr Williams.

'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,' he said.

'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.'

Having stepped down from his former job as Archbishop in December, Dr Williams said he was pleased to still be working with and for people living in poverty around the world.

'In the last few years as Archbishop of Canterbury I became more and more aware of the priority of development and aid issues worldwide,' he said.

'I wondered before I stepped down from office how best to carry on with the work that had really excited me and engaged me. So when the suggestion came to chair Christian Aid I was really delighted.

'I think it's very important that Christian Aid has a perfectly clear Christian vision animating and energising it. I think without that energy we wouldn't be where we are. It is an energy that overflows the boundaries, which says that all human beings are in the image of God, that all human beings have a dignity that needs respect.

'Christian Aid therefore is in a brilliant position to say yes of course we come from a Christian background and because of that we have no qualms about extending what we do, how we serve, how we partner with anyone and everyone.'

Dr Williams, who is also Master of Magdalene College Cambridge, begins as Chair less than two weeks before the start of Christian Aid Week which kicks off on May 12. This year's theme is 'Bite Back At Hunger'. For more information about Christian Aid Week, visit www.christian-aid.org.uk/caw.