Rishi Sunak has defended his controversial sex education plans after they were compared to Margaret Thatcher’s hated Section 28.
Ministers are to bar sex education classes for children younger than nine years old.
And the teaching of gender identity will be banned right up until the age of 18, education secretary Gillian Keegan said.
Critics have compared the plans to the heavily criticised Section 28 policy, which prohibited the promotion of homosexuality by local authorities, including in schools.
Earlier, Ms Keegan admitted ministers did not know how widespread the teaching of "inappropriate" material about gender identity was.
She told BBC Radio 4’s Today programme: "I don't think it's widespread, I mean, I don't know because you know, it's not something that we've gone and done a particular survey of."
She also said there had been "some evidence from some people" that pupils were being taught that there could be "72 genders" and gender could "change daily" as facts.
Mr Sunak said that what worried him was parents being kept in the dark and children “being exposed to things which you just thought, really is that the right age for them to be told certain things, discussing certain things.”
Grilled on the topic on ITV’s Loose Women, he dodged a question on what he had known about sex when he was 13, saying “I can't quite remember”.
But when it came to claims pupils were being taught there were 72 genders, he said: 'I don't remember that being an issue when I was younger.”
Labour said sex education should be age appropriate, but raised concerns over the new guidance.
Shadow education minister Cat McKinnell said that teaching children about the facts of the world in which they grow up had to include an understanding that there are people who are transgender.
But Ms Keegan insisted that discussion of gender reassignment would not be banned, adding: "Gender identity and ideology is something different."
Gender identity “should not be taught in schools at any age’’, she told MPs.
Labour MP Nadia Whittome criticised the plans, saying sex and relationship education was already taught in an age-appropriate way in schools. “The Tories claims about what children are learning are designed to fuel hysteria and build support for Section 28 style policies – which is what this latest guidance seems to be harking back to,” she added.
Sacha Deshmukh, the chief executive of Amnesty International, denounced the plans as “dangerous and put the safety and wellbeing of children at risk” as schools wrestle with issues such as children as young as seven being exposed to pornography.
He added: “A whole generation of LGBTI children and young people were left scarred by Section 28 - we should strive not to make the same mistakes again... Children of all ages have the right to a well-rounded education and should not fear discrimination. Schools need more resources, more training, and more support for teachers to deliver inclusive relationship, health and sex education which responds to the challenges children face today.”
The National Education Union have also warned the guidance fails to take into account that children and young people already get information about sex and relationships from the internet and in the playground.
Mr Sunak has been accused of stoking a culture war after the plans were leaked earlier this week.
It followed a major speech on Monday by the common sense minister Esther McVey who unveiled new civil service rules to end what she called “woke activism” in Whitehall and other departments.
