Pupils as young as five should be allowed to question the existence of God, new government guidelines recommend.
The long-awaited framework for RE - the first time a national code for the subject has been drawn up - says pupils should study secular philosophies at all key stages, alongside Christianity and other major faiths.
It also recommends that minority religions including Jainism, which promotes strict vegetarianism and believes all animals and plants have souls, should feature in syllabuses.
The code has been welcomed by The Church of England, Roman Catholics, the Muslim Council of Britain and the Board of Deputies of British Jews, who believe the subject has become increasingly marginalised by schools, leading to a drop in standards and a massive teacher shortage.
At the moment the subject must appear in the timetable of all pupils, unless parents opt out, but is not part of the national curriculum.
Instead, syllabuses are drawn up locally by committees of officials, teachers and religious groups. School governors draw up syllabuses in faith schools.
But critics of this system say that it has led to ad hoc provision with differing expectations and quality of learning across the country.
Launching the new code yesterday, Charles Clarke, the Education Secretary, said: "The framework is the starting place for considered and informed learning opportunities. Children have a right to be told about what is important to their friends who may hold different beliefs to their own.
Faith groups must seize this opportunity to develop their own resources that promote understanding of their faith, and their response to world issues."
Many are unhappy that the framework is voluntary. This week, the Qualifications and Curriculum Authority, which wrote the document, revealed that 98 per cent of teachers who were consulted said it should be made compulsory.
Mr Clarke said he would not rule out the possibility of adding RE to the national curriculum in the future. But any move to prescribe what is taught will be resisted by local advisers.
Sarah Smalley, chair of the Association of Religious Education Inspectors, Advisers and Consultants, said: "It is very important that we still have input at a local level to reflect the very different religious communities that exist across the country."
The report, which took a year to produce, says Christianity should be studied at every key stage. Other major faiths - Buddhism, Hinduism, Islam, Judaism and Sikhism - should be taught by the end of key stage 4. Minority religions, including the Baha'i faith, Jainism and Zoroastrianism, should also be studied.
The framework says that "where appropriate", children should have the opportunity to study secular views, including humanism, from key stage 1.
"Many pupils come from religious backgrounds but others have no attachment to religious beliefs," it says.
The move has delighted secularists. Marilyn Mason, of the British Humanist Association, said: "This recognises for the first time that some children don't believe and don't pray but their views should be accounted for."
The Professional Council for Religious Education, the subject association for teachers, said the framework represented a "landmark" for the subject but should be followed by more training and a teacher recruitment drive.
Last year there was a 6.6 per cent increase in the number of pupils taking GCSE RE, from 132,304 in 2003 to 141,037, in part down to the introduction of a new short course in the subject.
The annual report by David Bell, the chief inspector of schools, said many secondaries were breaking the law by failing to teach RE to 14 to 16-year-olds. He also said there was less specialised teaching in RE than any other subject.
Deborah Weston, chairwoman of the Professional Council for Religious Education, said: "The framework is only the beginning of what is needed. It cannot ensure that the shortage of RE teachers is resolved, or that those schools who fail to keep their statutory duty to provide RE for all pupils now do so."
ANOTHER VOICE 18
LAMPTON'S FOCUS ON 'EQUALITY AND RESPECT'
Ministers hope the framework will improve RE standards nationwide. But in many parts of the country, the subject is already a key part of the school day.
The Lampton school in Hounslow, London, is one of the first non-denominational secondaries in the country to be awarded specialist humanities status, with a particular focus on RE. Staff at the school, a typically diverse inner-city secondary, where a third of pupils are Muslim and the rest are a mix of Sikh, Hindu and Christian, insist RE is a perfect focus for "equality and respect".
At key stage 3 its 1,200 pupils study the major world religions and, importantly, also complete a section on humanism. In Year 11, pupils are expected to complete a full GCSE in the subject, and an A-level religious studies paper in philosophy and ethics is a popular sixth-form option.
Lawrence Carroll, the head of RE, said: "Children need to be educated in all faiths and non-religious beliefs to prepare them for the outside world."