Too much testing in schools risks killing the joy of reading for children, War Horse author Michael Morpurgo will say in a lecture later.
Schools are being pressured into "teaching literacy fearfully", Mr Morpurgo will tell an audience of publishers and educationalists.
More rigorous primary tests sparked parent protests in England this year.
Ministers say tests help identify pupils at risk of falling behind and need not be stressful.
But Mr Morpurgo says testing is "supposed to encourage" both those who pass and those who fail, but he will tell the inaugural Book Trust Annual Lecture at London's Guildhall that this is not the case.
"When you fail it brings only a sense of worthlessness and hopelessness.
"It brings fear and shame and anxiety.
"It separates you from those who have passed, rocks confidence, ruins self-esteem."
When you fail a test: "You disappoint yourself, disappoint others. You give up," Mr Morpurgo is expected to argue.
Tests help reinforce "almost an apartheid system of a kind in this country... Between those who read, who, through books, through developing an enjoyment of literature, can have the opportunity to access the considerable cultural and material benefits of our society - and those who were made to feel very early on that the world of words, of books, of stories, of ideas, was not for them, that they were not clever enough to join that world, that it was not the world they belonged to, that it was shut off from them forever."
He says too much government emphasis on "measurable outcomes and results" continues to reinforce a "great divide" that is "shamefully still there", with too many children still being failed.
"Our prisons are full of them... Many remain lonely and marginalised all their lives.
"The right book, the right author, the right parent, the right teacher, the right librarian at the right time, might have saved some of them at least, made the difference, shone a light into a dark life, turned that life around."
He is expected to call for:
- parents to read to their children every night
- a half hour "story time" at the end of the school day
- and a halt to library closures.
The testing system in England was changed this summer in line with a "new more challenging national curriculum" brought into England's schools in September 2014.
Ministers say it is vital that children master the basics of reading, writing and maths early on, so that they do not fall behind.
"Assessment has always been an important part of education - we know the tests are harder and we are asking more, but we're doing that because we are committed to ensuring opportunity for all," said a Department for Education spokesman.
"Tests should not be a cause of stress for pupils - they are there to help teachers understand where children may need more support and we trust teachers to approach testing in a proportionate manner."