MPs and parents have criticised a health survey in which children as young as 10 are asked if they feel the "same inside as the gender you were born with".
The Lancashire Care NHS Foundation Trust sent the form to schools across the county in north-western England asking children if they are "comfortable in their gender".
But one mother, Lyndsey Simpson, whose 10-year-old daughter brought home the letter, told the Telegraph: "I don't want someone putting into my daughter's head that she might not be happy with her own gender."
"It's one thing if they feel that way already, but if they don't, then do you want them to be unhappy for their whole lives?"
Parents had the option of not letting their children take part in the survey which they were told was simply aimed at helping healthcare workers and teachers "understand and support" children struggling with their identity.
But Tory MP and former childrens' minister, Tim Loughton, criticised the line of questioning.
"At a time when children are growing up and having to deal with all sorts of challenges of the modern world, now they are being asked to confront their gender, which for many will be unsettling," he told the Telegraph.
"Clearly we need to be sensitive about the issue of gender and sexual orientation but forcing children to question whether they are the right gender so early on can be deeply destabilising."
Jacob Rees-Mogg, a Conservative MP, described the question as "intrusive" and that "these are private matters in a family".
"These questions are not likely to be helpful. The child is too young – if they have these sorts of issues, the parents are the right ones to discuss it with, not a state survey," he told the paper.