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."
A Christian nursery nurse is claiming unfair dismissal after losing her job because she said she told a gay colleague that the Bible regards the practice of homosexuality as a sin.
Sarah Mbuyi says she only made the comments after being pressed on her beliefs by a colleague who initiated the conversation at Newpark Childcare in Highbury, north London, in January.
She is being supported in her case by the Christian Legal Centre, whose chief executive, Andrea Williams, said the Government has "seriously let down" the Christian community and criticised Prime Minister David Cameron for attempting to "mould Christianity to his political agenda".
Mr Cameron said earlier this week that Britain should be ''more confident about our status as a Christian country" and "more evangelical about a faith that compels us to get out there and make a difference to people's lives".
It is "easier to be Jewish or Muslim" in the UK than some secular countries, according to the Prime Minister.
David Cameron set out his Christian beliefs in an article for the Church Times and defended his faith by arguing that "tolerance" was one of its core values.
Many people tell me it is easier to be Jewish or Muslim in Britain than in a secular country precisely because the tolerance that Christianity demands of our society provides greater space for other religious faiths, too.
Crucially, the Christian values of responsibility, hard work, charity, compassion, humility, and love are shared by people of every faith and none - and we should be confident in standing up to defend them.
Her claim against her former employer was rejected as judges said Islington Council's action was "legitimate" given that it was obliged to consider the rights of same-sex couples. The Christian Institute, who supported her case said:
"Obviously, we are disappointed to have lost. But we are encouraged that two judges thought we should have won. What this case shows is that Christians with traditional beliefs about marriage are at risk of being left out in the cold."
"If the Government steamrollers ahead with its plans to redefine marriage, then hundreds of thousands of people could be thrown out of their jobs unless they agree to endorse gay marriage."