The UK Department for Education wants English schools to use the reading system, which requires children to blend common sounds into words.
But Durham University researcher Andrew Davis says those already starting to read are likely to be put off.
The UK DfE's 'One Size Fits All' policy, insists synthetic phonics is the best way to teach reading.
The teaching method encourages children to sound out words rather than recognising the whole word and reading it for meaning.
The government strongly encourages schools to use reading schemes based on synthetic phonics, and part-funds a range of books approved as meeting its criteria.
It has also introduced a phonics test for all Year 1 pupils to ensure they are using this method to decode simple words, as well as some made-up words.
It argues this is the best way to ensure no child falls behind with their reading.
But Dr Davis, a former primary school teacher, says in his pamphlet a small minority begin school able to read and understand sentences, while a larger group are able to recognise some words.
'Form of abuse'
He argues those well on their way to reading could be put off by reading books featuring only words for which they have been taught the phonetic rules in class.
He says: "To subject either the fully fledged readers, or those who are well on their way, to a rigid diet of intensive phonics is an affront to their emerging identities as persons.
"To require this of students who have already gained some maturity in the rich and nourishing human activity of reading is almost a form of abuse."
He agrees that phonics can be very useful for teaching reading, but argues it should not be rigidly imposed on all.
"Being forced to move back from reading for meaning to a mechanical exercise of blending and decoding is likely to be off-putting," he said.
He added that the fundamentalist approach to synthetic phonics "threatens the interests of a minority of children who arrive at school already able to read".
"The vast majority of Early Years teachers handle this kind of challenge with their usual professionalism, and will continue to do so if they are not troubled by rigid prescriptions from policy makers," he said.
A UK Department for Education spokeswoman said: "Too many children are not reaching the expected levels of reading at a young age, do not catch up, and then struggle in secondary school and beyond.
"Research shows overwhelmingly that systematic phonics is the most effective way of teaching reading to children of all abilities, enabling almost all children to become confident and independent readers.
"Thanks to the phonics check 177,000 six-year-olds will this year get the extra reading help they need to catch up with their peers."