Britain is now a "post-Christian" country, former Archbishop of Canterbury Rowan Williams has said.
Speaking to the Sunday Telegraph, Lord Williams said Britain was not a nation of believers and that the era of widespread worship was over.
It comes after Prime Minister David Cameron said people in Britain should be confident of its status as "a Christian country".
Deputy PM Nick Clegg said the Church and state should be separated.
Writing in the Church Times, Mr Cameron said Christians made a difference to people's lives and should be more evangelical about it.
This prompted a group of 50 public figures to write a letter insisting that the UK was "a non-religious" and "plural" society and that to claim otherwise fostered "alienation and division".
Lord Williams, who retired from being the leader of the Church of England in 2012, said: "If I say that this is a post-Christian nation, that doesn't mean necessarily non-Christian.
"It means the cultural memory is still quite strongly Christian."
He added: "But [Britain is] post-Christian in the sense that habitual practice for most of the population is not taken for granted.
"A Christian nation can sound like a nation of committed believers and we are not that. Equally, we are not a nation of dedicated secularists.
"It's a matter of defining terms. 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."
The current Archbishop of Canterbury, the Most Rev Justin Welby, has supported Mr Cameron.
On his blog he wrote it was a "historical fact (perhaps unwelcome to some, but true)" that UK law, ethics and culture were based on its teachings and traditions.