Parents' groups have attacked a plan to introduce compulsory sex education lessons, claiming that it disregards their views.
The Government has begun asking sex education and sexual health organisations how best to deliver personal, social and health education (PSHE) in schools.
This follows a recommendation last month by a Government-backed review that the subject should be made compulsory.
But the Family Education Trust claims that parents have not been consulted or asked whether they believe PSHE should be statutory.
Norman Wells, its director, said ministers had repeatedly refused to meet parents' groups.
"Parents are being excluded from the entire review process," he said. "It is outrageous that the Government should now be conducting a review that presupposes PSHE will be made statutory, without fully engaging with parental views and concerns."
Margaret Morrissey, of Parents Out Loud, agrees. She said: "A child in Hackney is probably going to benefit from a very different sex education programme from a child in Dorset. That's just a fact of life.
"Let schools consult parents. Let's go back to giving schools and parents the right to do things between them, so each school has its own way of doing things."
But the Department for Children, Schools and Families said the decision to make the subject statutory followed an extensive review of its teaching. The review group included governors and teachers, many of them parents.
A spokesperson said: "Parents bring up children, not schools or governments, but schools can help guide them through the maze of issues. We will ensure there is flexibility for schools to tailor lessons to reflect the values and beliefs of the parents they serve."