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."
His comments followed criticism of the Prime Minister's comments that the UK should be "more confident about our status as a Christian country" and "more evangelical" about faith.