The group New Millennium Challenge to the Churches says it has plans to entice people out of bed on a Sunday morning.
The campaign's organiser, the Rev Steve Chalke, said: "People in Britain are waking up to a different spirituality.
"There's a real spiritual hunger, which I believe will increase as the new millennium approaches. We have a 10-point challenge to all churches to make Christianity accessible to a new generation.
"We want churches to be family-friendly and relevant to society and if this involves altering traditional structures then that is the way forward. We are not looking for new converts, we just want to hold on to practising Christians."
Dr George Carey, the Archbishop of Canterbury, endorsed the new initiative.
"I strongly support this initiative and hope that as many churches as possible will be able to put this into practice," he said.
Canon Robert Warren, the author of Building Congregations, said: "People don't go to church because there are many more competing pastimes on a Sunday.
"And people are generally less responsive to being told what to think by an institutionalised religion. They also have access to a myriad of different philosophies, from self-help groups to new-age mantras and finally there is this cult of the individual. Going to church is about joining a community and that's not fashionable at the moment."
He added: "Christians believe there is still a lot of faith around, but people are just directing it at different sets of beliefs."
Just three million people - roughly 8 per cent of the population - regularly attend church on Sunday.
The Anglican and Roman Catholic churches have around one million regular attenders apiece, with the remaining denominations carving up the other million church-goers.
Since 1980, the Roman Catholic church has lost 600,000 attenders, compared with a 100,000 decline in the Anglican church.
Tom Horwood, a spokesman for the Roman Catholic church, said: "A lot of organisations are suffering declining numbers because people don't like joining things anymore.
"Even the St John's Ambulance and the Neighbourhood Watch have lost a lot of members. Many people say they are Christian and believe in Christianity, but they don't go to church regularly to prove it."Reuse content