Education Secretary Michael Gove's proposals for a new national curriculum were condemned as "fatally flawed" on by an expert who advised him on the overhaul.
Planned changes to what primary school children are taught in English, maths and science are too detailed and do not take into account the needs of pupils, according to Professor Andrew Pollard.
Prof Pollard was a member of the expert panel appointed by Gove last year to advise on the review of the national curriculum.
Writing on an Institute of Education blog on Wednesday, Prof Pollard said the new curriculum is "constraining" and leaves little room for teachers to exercise their professional judgment.
His comments come the day after the Department for Education unveiled new draft curricula for English, maths and science in primary schools.
The changes, which have been published for an informal consultation, focus on a back-to-basics curriculum, with pupils expected to memorise their times tables up to 12 by age nine, multiply and divide fractions by age 11 and begin to learn and recite poetry at five.
The expert panel published its recommendations in December, and Pollard was not involved in working on the programmes of study published on Tuesday.
In his blogpost, Pollard said Gove's instructions to the chair of the expert panel, Tim Oates, were to "trawl the curricula of the world's highest-performing countries, to collect core knowledge and put it in the right order".
He questions why he was appointed to the panel as he was unlikely to go along with this "crude design for curricula reform".
"For my own part, I would not deny that subject knowledge is important nor demur from sustained efforts to consider how it should be most appropriately represented in a programme of study," Pollard writes.
"And of course, the idea sounds wonderful - yes, let's sort out, once and for all, when spelling of particular words will be mastered, and the use of apostrophes, and the subjunctive, and so on. So this approach is likely to be very attractive to the public.
"But the approach is fatally flawed without parallel consideration of the needs of learners."
On the basis of the government's proposals, teachers will be faced with "extremely detailed year-on-year specifications in mathematics, science and most of English," Pollard says.
"This is to be complemented by punitive inspection arrangements and tough new tests at 11. The new curriculum will preserve statutory breadth, we are told, but whilst teaching of a foreign language is to be added, provision for the arts, humanities and physical education is uncertain at this point.
"The constraining effects on the primary curriculum as a whole are likely to be profound and the preservation of breadth, balance and quality of experience will test even the most committed of teachers."
The expert panel had recommended that the curriculum in these subjects be organised into two-year blocks, to give teachers room to use their judgment and take account of children learning at different rates, he said.
Pollard added that the government's proposals should now be subjected to scrutiny by teachers, researchers and others.
Shadow education secretary Stephen Twigg said: "The fact that an expert adviser to the government on the national curriculum has called Michael Gove's plans 'fatally flawed' is highly embarrassing.
"It now seems that after commissioning an in-depth review, the Government is ignoring many of its recommendations in favour of its own prejudice.
"The government should put evidence ahead of dogma when it comes to education. The curriculum mustn't be prey to political ideology."
Oates, who is still working with ministers on the new curriculum, said Pollard's concerns were "misplaced".
"The principles agreed with the expert panel, including Andrew, at the start of the review remain in place," he said.
"There is greater demand and detail in the content of these key subjects and there is greater freedom for teachers in how they teach it.
"Publishing content year by year is not some rigid straitjacket. There remains flexibility for schools in the scheduling of content.
"The draft programmes of study are drawn from a rigorous research base, both domestically and internationally. The frameworks of 18 jurisdictions were considered in unprecedented detail.
"The resulting programmes - now out for informal consultation before a further formal consultation - align us with the best education systems in the world."
