The parents of a four-year-old boy withdrew him from his school’s World Book Day in a row over what they claimed were “confusing and harmful” gender identity lessons.

Stephen and Joanne Evans objected to the book My Shadow is Pink, saying it could plant the idea in young minds that children might be born into the wrong body.

They claim the book, by Scott Stuart, promotes the concept of an inner gender identity that is a child’s true self, and what a child wears and the things they like to do affects the sex they were born into.

The book, which is sold as appropriate for three-year-olds, explores the world of a boy who feels uncomfortable with male stereotypes. In it the father tells his son: “Your shadow is pink, I see now it’s true, it’s not just your shadow, it’s your innermost you.”

When Mr and Mrs Evans were told their child’s class would be using My Shadow is Pink for World Book Day last Thursday they asked for permission to withdraw him from St Mary’s Church of England Primary School, in Southend-on-Sea, Essex, for the day.

They say other parents also raised their concerns about the book being used.

The policy group Transgender Trend has criticised My Shadow is Pink as one of a number of books for primary school children that promote the "idea that changing appearance through opposite sex clothes and hair length changes natal sex”.

Mr and Mrs Evans said: “As soon as we saw what was being planned on the class app, we were shocked and knew something was not right.

“We are not alone in believing that the book is confusing and is not appropriate for four-year-olds, especially in a Christian school. Christian and non-Christian parents have raised concern, but the head teacher has ignored it.”

They added: “Parents who believe we are born male and female and who do not want their children exposed to harmful ideology are losing their voice and their rights.

“We want the CofE hierarchy to step in and do more to protect the rights and beliefs of, not just Christian parents, but all parents who do not want their children exposed to transgender propaganda.”

Mr and Mrs Evans, who are supported by Christian Concern, have now written to the Church of England’s chief education officer, Nigel Genders, to raise the issue.

The St Mary’s headteacher, Aleishia Lewis, granted Mr and Mrs Evans permission to withdraw their child for the day, but defended the use of the book for primary school children as encouraging the idea that difference is a positive thing.

In a letter to the couple, Mrs Lewis said: “The primary focus of the story is not gender identity. The boy in the story doesn't change his gender, nor is there any reference to him wanting to. The main theme of the book, as referenced by the author himself, is one of gender stereotyping and the book was written when his own son came home upset after being told by another child that he couldn’t wear an Elsa dress at nursery because he was a boy.”

Mrs Lewis added: “The very fact that the shadows are pink and blue are a stereotype in itself and reinforces a concept that is present within even our youngest children in Reception. The Dad in 'My Shadow is Pink' demonstrates that acceptance comes from a place of love and we want every child in our school to recognise that they should show love to others in the same way.”