The Coalition for Marriage has condemned a new BBC resource for children aged 9 to 12 claiming that there are more than two gender identities.
In a new BBC Teach video, Relationships and Sex Education teacher Kate Daniels can be seen telling two children that there are "so many gender identities".
"So we know we've got male and female, but there are over 100, if not more, gender identities now," she said.
She added: "You've got some people who might call themselves gender queer, who are just like 'I don't really want to be anything in particular, I'm just going to be me.'"
In another segment, a little boy asks "what are the different gender identities?", to which a head teacher named Kyra replies, "That's a really, really exciting question to ask."
The video is part of the Big Talk series by BBC Teach to support PSHE (Personal, Social, Health and Economic) lessons in schools.
It has been strongly criticised by the Coalition for Marriage, which called it "incredibly dangerous".
"The nonsensical claim is included in a new BBC Teach video series for 9-12 year olds which is supposed to help teachers 'deal with sensitive subjects in an age-appropriate... and honest way'. It does neither," it said.
"The reality is transgender ideology causes pain and suffering," it added.
The Telegraph columnist Celia Walden, who is married to Piers Morgan, has also expressed her anger at the resource.
She said it was the "journalistic duty" of the BBC "to deal not in fads, but facts" and that the "noxious nonsense" in the video series was "likely to leave us with a generation of lost, confused and angry young adults asking a question we will find it very difficult to answer: 'How did you let this happen?'"
"How dare the BBC teach children that there are '100 genders'?" she wrote in The Telegraph.
"Even by today's Emperor's New Clothes gender diversity narrative, 100 is pushing it. 'Woke' Facebook currently lists 71 complex and hilariously repetitive options for those who feel manacled by the oh-so-reductive'male' and 'female'."