Only 12 per cent of children in the UK are now baptised, and there has also been a collapse in the number of Church weddings, a leading Church of England bishop has warned.
And the Church of England could die out within a generation if the problem isn't tackled, according to Rt Rev Paul Richardson.
In an article in the Sunday Telegraph, Bishop Richardson said that Britain was “no longer a Christian nation”.
He highlighted figures showing that the number of babies being baptised has fallen from 609 in every 1,000 at the turn of the twentieth century to only 128 in 2006/7. Church marriages have also dropped, he said.
As one of the Church's longest-serving bishops, the comments by the assistant Bishop of Newcastle are set to fuel the debate over its future.
The General Synod, the Church of England's parliament, will next month consider proposals to cut the number of bishops and senior clergy amid fears over the Church's finances.
Bishop Richardson said: "Many bishops prefer to turn their heads, to carry on as if nothing has changed, rather than face the reality that Britain is no longer a Christian nation.
He said that the Church had lost more than one in ten of its regular worshippers between 1996 and 2006, with a fall from more than one million to 880,000.
"At this rate it is hard to see the church surviving for more than 30 years though few of its leaders are prepared to face that possibility," said Bishop Richardson.
Nearly half of the population in England regard themselves as belonging to the Church of England, while seven in ten described themselves as Christian in the last census.
However, the Bishop said that the fall in church marriages and baptisms revealed that Britain was no longer a Christian nation.
Bishop Richardson said: "The church is being hit by a double whammy: on the one hand it confronts the challenge of institutional decline but on the other hand it has to face the rise of cultural and religious pluralism in Britain."
He says that the way the Church responds to this will be "crucial in determining whether it will be able to survive as a viable organisation and make a contribution to national life".
"At present church leaders show little signs of understanding the situation. They don't understand the culture we now live in."
Lord Carey, the former Archbishop of Canterbury has also delivered a bleak assessment of the future of Christianity in this country, claiming previously that Britain's Churches are in such serious decline that if they were shops they would have been declared bankrupt long ago.
Attendance figures on Christmas Day and Christmas Eve have provided encouragement for the Church of England, showing that three million people attend services on these days and as many as 39 per cent go to some sort of Christmas service.