Disappointing figures in the 2011 Census have prompted calls for the church in England and Wales to find new ways of engaging.
Norman Ivison, of Fresh Expressions, said the Census figures showed "what many have been saying for some time".
Data released this week revealed a considerable drop in the number of people in Britain describing themselves as Christian, down from 72% in 2001 to 59% in 2011.
Meanwhile, the number of Muslims has risen from 1.5 million to 2.7 million - or 5% of the population - while the number of people describing themselves as having no religion rose by 10% to 25% of the population.
"The church in England and Wales needs to find new ways of engaging those who no longer have, or never had any interest in the Christian faith," said Mr Ivison.
Fresh expressions of church are being pioneered across the UK. Forms of fresh expressions include cafe churches, children's churches and meetings in pubs.
"The reality is that inherited church life is still attractive to many people but not to everyone," said Mr Ivison.
"New forms of church are developing throughout the UK, alongside parish and other traditional structures, which are increasingly helping those who have never been to church to discover the Christian faith for themselves.
"The Census statistics demonstrate that real alternatives need to be offered for those who find conventional church inaccessible for all sorts of reasons."