Parents are "right to be concerned" about the Welsh Government's plans to make sex and relationship classes compulsory for all children, The Christian Institute has said.
The Welsh Government wants to remove the right of parents to withdraw their children from RSE lessons when the new curriculum is rolled out in primary schools and the first year of secondary in 2022, and then for students up to 16-years-old in 2026.
This is despite the Welsh Government's consultation finding strong opposition to the plans, with 89% of respondents supporting the right of parents to take their children out of classes.
The proposals are being put once again to the public in a fresh consultation inviting responses until November 28.
The new curriculum will teach children about relationships, gender, sexuality and sexual behaviour, with the consultation paper promising that lessons will be "developmentally appropriate".
"Developing RSE through different areas of learning and experience within the new curriculum gives learners a rich and wide-ranging view of human relationships and sexuality from a variety of disciplines," it states.
Respondents are also asked for their views on removing the right of withdrawal from RE lessons and changing the name of these classes to "Religions and Worldviews".
This "appropriately reflects teaching practice within the new curriculum, and allows for the exploration of a range of religious and philosophical beliefs, as well as other beliefs and world-views, including non-religious world views", the consultation paper argues.
John Denning, Education Officer at The Christian Institute challenged the Welsh Government on why it was consulting again on the question of parents' opt-out rights.
"Many people would regard the Welsh Government's decision to consult the public then ignore them as contemptuous," he said.
"And parents are right to be concerned about whether the sort of material and beliefs likely to be forced on pupils are really appropriate for their own children.
"The existing right of withdrawal has historically been rarely used but is an important backstop protection which discourages schools from adopting radical approaches."
He pointed to reports of alarming new primary school material developed by Warwickshire County Council that includes graphic images, lessons on self-touch, and sections on transgenderism that he said parents will "rightly worry could be harmful to children".
The content of the lessons prompted Christian couple Matthew and Naomi Seymour to withdraw their children.
"So the idea that the Welsh Government can be certain that schools will always be right and that parents' views are irrelevant is actually pretty arrogant," Mr Denning said.
"We would urge the minister to listen to the concerns and comments of those who took the time to take part in her consultation."
Sian Rees, director of the Evangelical Alliance in Wales, told the BBC that parents should have the right to take their children out of RSE lessons.
"We believe that age isn't an indication of maturity and that these conversations are conversations that should perhaps be occurring within the home," she said.
"The [new curriculum] framework as it stands is very vague. We would ask the minister to provide more clarity and explanation as to what exactly she would like teachers to cover."