Lord Carey, the former Archbishop of Canterbury, has warned that Christianity is "a generation away from extinction" in Britain.
Christianity is close to extinction in Britain unless churches make a dramatic breakthrough in attracting young people back to the faith, Carey has warned.
Clergy are now gripped by a "feeling of defeat", congregations are worn down by "heaviness", and the public simply greets both with "rolled eyes and a yawn of boredom", he said.
His comments at a conference came as a stark report laid before the Church of England's General Synod warned that its position as a "national institution" would be in doubt if numbers in the pews dropped much further.
The Archbishop of York, Dr John Sentamu, also underlined the scale of the crisis, telling members of the Synod they must "evangelise or fossilise".
In an impassioned plea for the Church to adopt a new missionary stance, he told them that their constant internal debates were no more than "rearranging furniture when the house is on fire".
He called for a campaign aimed at the "re-evangelisation of England", on a par with the ministry of the northern saints such as Cuthbert, Hilda and Aidan, who spread Christianity in Anglo-Saxon times.
The Synod responded by voting to set up a committee.
Carey's warning came as he addressed the Shropshire Light Conference at Holy Trinity Church in Shrewsbury at the weekend, discussing how the church could be "reimagined".
The former Archbishop said while the church is doing much important work, it faces an existential challenge.
"In many parts of Britain churches are struggling, some priests are diffident; a feeling of defeat is around.
"The burden seems heavy and joy in ministry has been replaced by a feeling of heaviness."
He said the reaction from the public was not so much hostile as dismissive.
"The viewpoint could be expressed in a variety of non-verbal ways: the shrug of indifference, the rolled eyes of embarrassment, the yawn of boredom.
"So many people do not see the average church as a place where great things happen.
"To sit in a cold church looking at the back of other people's heads is surely not the best place to meet exciting people and to hear prophetic words."
He added: "It is still the case that people are essentially looking for spiritual fulfilment.
"One of the most worrying, most urgent groups we need to invest in is young people."
He warned against relying on "more gimmicks" to revive the Church's fortunes, adding: "The most urgent and worrying gap is in young people's work.
"So many churches have no ministry to young people and that means they have no interest in the future.
"We have to give cogent reasons to young people why the Christian faith is relevant to them."
His comments came as a report was laid before the Church of England's General Synod, warning that plunging congregations now threaten its ability to "sustain a nationwide presence".
Typical Sunday congregations have almost halved since 1970 to just 807 000 in the most recent figures.
