Lord Williams, the former Archbishop of Canterbury, has declared Britain a "post-Christian" country in an interview with The Telegraph.
Lord Williams of Oystermouth, who stood down as leader of the Church of England in December 2012, said that while Britain's "cultural memory is still quite strongly Christian", it is "post-Christian" in its practice.
"A Christian nation can sound like a nation of committed believers, and we are not that," he said. "Equally, we are not a nation of dedicated secularists.
He added: "A Christian country as a nation of believers? No. A Christian country in the sense of still being very much saturated by this vision of the world and shaped by it? Yes."
Asked whether Britain will lose its faith altogether, he said: "Given that we have a younger generation now who know less about this legacy than people under 45, there may be a further shrinkage of awareness and commitment."
The outgoing Archbishop of Canterbury has warned his successor that "risking unpopularity" is a crucial part of the job.
Dr Rowan Williams, who leaves the post tomorrow, said, "Risking unpopularity, taking the flak, is what Archbishops are here for - it is the stuff of the job".
"It is something you realise the more you work here, that maybe Britain benefits from having someone to get angry with, and that compared to my predecessors I have got off lightly”, he said in an interview for BBC Two documentary Goodbye to Canterbury, according to The Daily Telegraph.
Dr Williams was often criticised throughout his tenure for being outspoken. In 2008, the Archbishop's comments that the adoption of some aspects of Islamic Sharia law "seems unavoidable" were condemned by many.
His successor, Bishop of Durham the Rt. Rev. Justin Welby, will take over the post in March.
The Archbishop of Canterbury Dr Rowan Williams has said the Church of England has "undoubtedly" lost a "measure of credibility" in wider society following the defeat of the legislation to introduce women Bishops to the church.
He told the General Synod: "Whatever the motivation for voting yesterday whatever the theological principle on which people acted and spoke, the fact remains that a great deal of this discussion is not intelligible to our wider society.
"Worse than that, it seems as if we are wilfully blind to some of the trends and priorities of that wider society.
"We have some explaining to do, we have as a result of yesterday undoubtedly lost a measure of credibility in our society."
The Archbishop Rowan Williams used his final Easter address to talk about the place of religion in society and in education. He said that despite the public debate about the "usefulness" and "social value" of religion, it is worshippers' personal relationship with God that matters.
The Archbishop of Canterbury Rowan Williams will talk about religious education in schools when he gives his Easter sermon today. He will say:
There is plenty to suggest that younger people, while still statistically deeply unlikely to be churchgoers, don't have the hostility to faith that one might expect. They at least share some sense that there is something here to take seriously when they have a chance to learn about it. It is about the worst possible moment to downgrade the status and professional excellence of religious education in secondary schools.