Half of the Westminster government's four-strong panel of expert national curriculum advisers were so concerned that the proposed changes would be too prescriptive and lacked trust in teachers that they tendered their resignations, TES has revealed.
Drafts of a new primary curriculum in English, maths and science were published last week and immediately ran into controversy as a row between the advisers over their contents exploded in public.
Misgivings within the panel ran so deep that in October two of the advisers, professors Mary James and Andrew Pollard, wrote to education secretary Michael Gove to resign. Their joint letter warned that some aspects of the government's curriculum review "fly in the face of evidence from the UK and internationally and, in our judgement, cannot be justified educationally".
But Tim Oates, chair of the expert panel, said that their fears were premature and unwarranted.
Mr Gove persuaded the pair to stay on until December after meeting some of their concerns. But their resignations were only withdrawn on condition of being able to distance themselves from the draft primary programmes of study released last week.
Their letter alleged that thousands of "stakeholder" consultation responses "appear to be treated lightly", whereas "significant influence" had been exercised by schools minister Nick Gibb.
"The use of evidence has been uneven," it added. "We are concerned for the perceived legitimacy and quality of the review."
Most damaging was criticism of the year-by-year structure, which remains in the new draft primary curriculum for English, maths and science, implicitly suggesting that the government has failed in its stated aim of producing a curriculum to set teachers free.
But Mr Oates said his fellow experts' fears were unjustified and did not take into account greater freedom that would be offered in other subjects or the fact that the year-by-year structure would not be mandatory.
Responding to claims from Professor Pollard that the review's approach was "fatally flawed", Mr Oates said: "It is a conflict, there are disagreements and Andrew is not right."
Mr Gove revealed last week that foreign languages would become compulsory from the age of seven.
The three big teaching unions said that the draft primary programmes of study were too prescriptive.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said that they would result in "rote learning" and contain such a weight of detail that the idea of there being more space for freedom in other subjects was "nonsensical".
But Russell Hobby, general secretary of the NAHT heads' union, said: "An increase in prescription in the core subjects and more freedom in the rest is a good trade to make."
The resignation letter of the professors can be read at http:bit.lyLTguAY
Much of the maths in primary will remain the same, but there is a definite acceleration, especially in early primary.
The programme of study expects children to know the pairs of numbers that add together to make 20 in Year 1 (P1), rather than Year 2 (P2). By Year 4 (P4), pupils should have been taught multiplication tables up to 12x12 rather than 10x10. In Year 6 (P6), binary notation up to 15 (1111) is introduced.
Progression in numbers is mostly accelerated rather than widened, although there are some new additions, such as being able to read Roman numerals.
Evolution will be specified in the science curriculum for the first time - and pupils will learn about the life of Charles Darwin, alongside other key scientific figures such as William Harvey and Sir Isaac Newton.
In key stage 1, proposals include learning to name common birds, fish, amphibians, reptiles, mammals and invertebrates. The guidance even suggests children collect snails - but return them safely to their environment afterwards.
At key stage 2, pupils will learn about the solar system and galaxies, with accompanying guidance suggesting Year 4 (P4) pupils could learn to recognise and name some constellations. The current science curriculum only insists on pupils studying the Sun, Earth and Moon.
There will be an increased focus on practical scientific experiments - but the requirements in Years 1 and 2 (P1 and 2) have been scaled down and the Institution of Engineering and Technology has raised concerns, saying that there should be more focus on young children's enthusiasm for practical science.
The draft English curriculum includes reciting poetry, learning a list of 235 spellings and phonics.
The new curriculum emphasises the importance placed on the phonics strategy, which helps pupils decode language and includes checks on how well children can read both real and made-up words. The three main teachers' unions in England this week urged MPs to rethink phonics checks on six-year-olds, describing the tests as "flawed".
The draft English programme includes guidance that pupils "practise their reading with books that are consistent with their developing phonic knowledge and that do not require them to use other strategies to work out words".
But it also talks about the importance of reading whole books to pupils, discussing and debating works and developing a love of literature.
The importance of speaking skills is included in the introduction, but there is no separate strand of study as before.