In a joint statement, the Church of England and the Roman Catholic Church said the new curriculum neglected to teach young people spiritual and moral values.
The curriculum, published in May, will be compulsory for all children aged 5 to 16 from September 2000. The statement from the Church of England Board of Education and the Bishops' Conference Department for Catholic Education and Formation says: "We are dismayed that the framework does not contain a single reference to marriage or to the primary responsibility of parents for the education of their children."
Margaret Smart of the Catholic Education Service said: "What is going on? Do different ministers think different things? We have Jack Straw, the Home Secretary standing up and saying marriage is the most secure way of providing for children. Then you have the curriculum for personal, social and health education ignoring it. It mentions divorce and it mentions separation but not marriage. It really is incomprehensible."
Both churches are concerned that a statement of shared values, worked out two years ago by a forum of experts from education, industry and the churches and organised by government curriculum advisers, does not appear in the new curriculum.
That statement said people should support the institution of marriage. Ms Smart said that, without such a statement, moral issues became "simply a matter of personal opinion."
There was no rationale underpinning teaching in citizenship or in personal, social and health education, she added.
The churches' statement quotes the late Cardinal Basil Hume who said: "If the adult world cannot agree on the way we should live in society, how can we expect the young generation to know?"
The Rev John Hall, the Church of England's director of education, said: "We support the literacy and numeracy strategies but if there is no clear reference to the importance of spiritual and moral development, they will be sidelined."
The churches say they are worried that spiritual instruction will be confined to religious education lessons whereas it should be taught in all lessons.
A Department for Education spokeswoman said: "There is no downgrading of spiritual and moral values. Teaching about them has been strengthened because we are including them in citizenship, which will be part of the national curriculum for the first time." She said a consultation document on personal, social and health education issued last month did mention marriage. This was not part of the curriculum but all schools had to teach it.Reuse content