Christian parents say they were left with no choice but to remove their son from a Church of England primary school's World Book Day events after finding out about the use of a gender identity-themed book.

Stephen and Joanne Evans' four-year-old son attends St Mary's Prittlewell Church of England Primary School, in Southend-on-Sea.

They say that the school planned to use the book My Shadow is Pink, by Scott Stuart, as a "stimulus" for activities marking World Book Day on 2 March and that parents were not consulted about it beforehand.

In one passage in the book, geared towards pre-school children, the father says to his son: "Your shadow is pink, I see now it's true, it's not just your shadow, it's your innermost you."

The Evans asked for permission to withdraw their son, which was granted, but they say that in response, the head teacher also suggested they read the Church of England's school policy, Valuing All God's Children, and resources from Living in Love and Faith, including the bishops' support for a "radical new Christian inclusion".

The Evans, who are being supported by Christian Concern, have written to the CofE's chief education officer, Nigel Genders, about their concerns. The Church of England confirmed that Genders received a letter from the Evans and that a reply will be sent "in due course".

In a statement, the parents said they were "shocked" by the material being used in lessons.

"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 said.

"We want to know where teaching this book will lead next and where the school draw the line. Parents have not been properly consulted and it looks like we and are our children are being placed on a 'woke' conveyor belt.

"The CofE's own guidance being used against us to justify confusing and harmful teaching on gender identity is a slap on the face.

"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."

Andrea Williams, chief executive of Christian Concern, said: "If ever there was a moment in history for those responsible for Church of England schools to wake up and return to biblical teaching it is now. How can anyone think this book is a good idea, let alone the Church?

"It is another example of the Church of England hierarchy's lack of confidence in the gospel they are there to promote and which has actually given their schools such outstanding reputation.

"This book, and the many others like it that are being introduced often without parents' knowledge or proper consultation, have no place in primary schools, let alone Christian ones.

"Christian parents who believe we are born male and female are increasingly being silenced or told that they are 'transphobic' if they do not want their young children to be exposed to harmful and confusing transgender ideology.

"Consistently, the Church's own guidance on these issues is being used to silence parental dissent. This is a travesty which must urgently be resolved."

A spokesperson for the Diocese of Chelmsford said: "Like all Church of England schools in the Diocese of Chelmsford, St Mary's Prittlewell C of E Primary School follows Government and Church of England guidance in their teaching. They work closely with and communicate well with parents about sensitive topics in the curriculum and did so on this occasion. As Mrs Lewis has explained, the theme of their World Book Day was stereotypes and not, as has been suggested, gender identity. Stereotypes is an important topic within the PSHE national curriculum and their World Book Day teaching reflected this."

St Mary's Prittlewell Church of England Primary School said in a statement:  "St Mary's Prittlewell C of E Primary School follows Government and Church of England guidance in our teaching. We work closely with and communicate with parents about sensitive topics in the curriculum and did so on this occasion, making parents aware of our plans and offering to meet with anyone with concerns. We always listen to concerns and did so on this occasion.

"The boy in the story does not change his gender nor is there any reference to him wanting to. The primary focus of the book is self-acceptance and challenging stereotypes which are important themes that form part of the PSHE national curriculum for children from Reception to Year 6. Stereotypes can affect every part of life, contributing towards poor mental health in young people, higher suicide rates, low self-esteem and issues with body image."

Editor's note: This article was updated on 7 March to include statements from the Diocese of Chelmsford and St Mary's Prittlewell Church of England Primary School.