The Christian Institute has voiced concern over reports that teaching on gender is affecting the grading of schools by Ofsted.
The Telegraph reports that schools have been downgraded by the regulator over a lack of teaching on "gender diversity", "gender reassignment" and "gender identity".
The newspaper analysed pre-Covid inspections and found that this issue featured "prominently" in the reports of several schools that failed to receive the top grade.
The Christian Institute's Education Officer John Denning said it was wrong to downgrade schools over their refusal to promote radical transgender ideology.
Mr Denning said: "Ofsted has had a long history with Stonewall, causing major problems for some schools with a religious ethos and pushing a skewed approach in all schools.
"The content of the curriculum is exempt from the Equality Act but academies and fee paying schools in England are required by separate legislation to promote principles which encourage respect for other people, paying particular regard to the nine protected characteristics set out in the Equality Act.
"Promoting respect for people is not the same as promoting Stonewall's view on the two protected characteristics of sexual orientation and gender reassignment, the only ones on which Ofsted generally comments. Doing so breaches schools' duties of political impartiality and respect for parents' and children's beliefs.
"Statutory guidance on Relationships and Sex Education also tells schools they should 'teach about LGBT', but that it is up to them to judge when to do this. There is no requirement it is covered in primary schools."
The inspections analysed by The Telegraph pre-date Osted's decision to leave Stonewall's controversial pro-trans 'Diversity Champions' scheme last year.
The Christian Institute said the newspaper's findings were evidence of the influence of "Stonewall dogma".
Mr Denning added, "It's about time Ofsted started focussing on inspecting schools' compliance with English law, not 'Stonewall Law'."
