The Church of England lost 100,000 worshippers between 2000 and 2002, according to figures that will make gloomy reading for the clergy.
The decline of nearly eight per cent is greater than some statisticians expected.
Figures show signs of growth in attendance among the young
In 2002 the average number of people attending a church at least once a week was 1,166,000, down from 1,274,000 two years earlier, the Church's provisional figures show.
The average number going to a service on Sunday but not during the rest of the week was 1,002,000, down from 1,058,000 in 2000. Between 2001 and 2002, one diocese lost 5,600 weekly worshippers and another lost 4,700.
But the Church said there were signs of growth among young people, with the average number of under-16s attending church at least once a month increasing by one per cent between 2001 and 2002.
"It is evidence for the first time in a long time that the rapid decline in the numbers of young people going to church may have stopped," a Church of England spokesman said.
Peter Brierley, the executive director of Christian Research, an independent organisation, said the overall drop was "worrying" and needed urgent attention. Dr Brierley, a former Government statistician, predicted that the decline could speed up after about 2020 when ageing churchgoers died.
He said his research suggested that smaller churches tended to do better than larger ones. A few churches, mostly evangelical, were growing.
The Church's official figures show that a number of dioceses, including London, Exeter and Manchester, added to their numbers between 2001 and 2002.
Others suffered dramatically. Blackburn lost 3,000 worshippers at weekly services, Liverpool lost 3,000, Lichfield 4,700 and Chester 5,600.