A gay MP called on the prime minister to condemn the leader of the House of Commons over comments she made about LGBT education.
Lloyd Russell-Moyle criticised Andrea Leadsom after she said parents should decide when their children were "exposed" to the lessons.
He also attacked "bigots that don't want LGBT people to be heard in schools".
Some Birmingham schools have stopped LGBT rights classes after protests.
Parkfield Community School, in the city, said it would not resume the lessons until a resolution had been reached with parents.
In a statement on Wednesday, the school said it was planning to "evolve" its equalities teaching "in collaboration with parents".
Ofsted said previously that Parkfield's lessons about LGBT rights and homophobia were age-appropriate.
Campaign group IslamicRSE told the BBC's Asian Network it was behind a nationwide campaign to encourage Muslim parents to withdraw their children from same-sex relationship education lessons in primary schools, and had circulated 350 letters around Greater Manchester.
Speaking during Wednesday's Prime Minster's Questions, Mr Russell-Moyle, Labour MP for Brighton Kemptown, said Ms Leadsom's comments about parents choosing when certain education was introduced was "Conservative party dog-whistle politics".
"I know the prime minister campaigned to keep Section 28, which banned LGBT people being talked about positively in schools, and led to millions of young people, like myself, growing up in fear of being LGBT," he said.
"I thought the prime minister had seen the error of her ways, but this morning the leader of the house said on radio that parents should decide when they [their children] are exposed to LGBT education."
He also called on Theresa May to "support Ofsted with good LGBT education in our schools".
Labour's Lloyd Russell-Moyle urges PM to "condemn bigots that don't want LGBT people to be heard in schools", saying he grew up "in fear of being LGBT"#PMQs updates: https://t.co/g4OVIZWCgr— BBC Politics (@BBCPolitics) March 20, 2019
More on schools LGBT row: https://t.co/6jL3kLLt6X pic.twitter.com/obD49Ew6Jl
PM Theresa May told the Commons the government "has been at great pains to ensure that appropriate guidance is given to schools".
She said she would write to Mr Russell-Moyle about the official guidance Ofsted provides for teaching about LGBT relationships.
During an interview on LBC radio, Ms Leadsom said: "I think it is right that government should have passed legislation that requires that relationships and sex education is taught in schools, but at the same time I also agree that it is right that parents should be able to choose the moment at which their children become exposed to that information."
Ms Leadsom also said she was a "massive supporter of the efforts that we've made to achieve real equality in LGBT rights".
"It's absolutely vital that children do grow up understanding the society that they live in, and that they grow up tolerant and seeking equality and respecting differences," she added.
By Sima Kotecha, Midlands Correspondent
Political intervention from both sides of the House of Commons has inflamed the debate.
But for the protesters and the schools involved, it's perhaps a relief to know that people in positions of power are listening and engaging.
Views are passionate - and anger is rife.
Those who are adamant that homosexuality is morally wrong strongly feel that the Equality Act should protect their religious beliefs.
However, for the LGBT community, "alarmed" is the word often being used to convey feeling both here in Birmingham and around the country, and they believe their human rights are being abused by schools who have stopped teaching children about same sex couples.
And now the row is spreading. In Greater Manchester, the BBC understands hundreds of parents have sent letters to schools asking for their children to be removed from sex education lessons.
As the dispute escalates, so does the tension around this controversial topic.
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