Jane Williams, the theologian and wife of the Archbishop of Canterbury, suggested last night that the traditional model of the family promoted by the church might be outmoded in tackling modern social problems.
She called on churches to do more to support families and to relieve modern pressures by helping them become part of a wider social structure.
In a speech to the Mothers' Union in London, Mrs Williams, who had hitherto kept a low public profile, implicitly criticised the insistence of politicians, and some churchmen, that families are the bedrock of society, saying too much pressure was placed on parents to be all-sufficient.
In words that may alarm some Christians, she said there were other examples of faithfulness and commitment than the westernised nuclear family.
"If war and Aids have ravaged the shape of families in much of the world, unfaithfulness and divorce have done the same in this country. Too many of our children are growing up with no models at all of lasting, committed relationships, either in their family or the community around them.
"What chance will they have of building for themselves something they have never seen? We urgently need to think imaginatively about how children might be grounded in wider sets of social relationships that will nurture them and help them to believe that relationships can work and last," she said.
"Our lives together need to demonstrate how people might live together in faithfulness, commitment and love ... but some Christian communities are inward looking and too ready to condemn rather than inspire.
Mrs Williams is the first archbishop's wife in nearly 150 years to bring up young children at Lambeth Palace.