Pupils are encouraged to talk about intimate sexual acts in a game featured in a toolkit for schools.
The toolkit, created by the Proud Trust, includes a game involving a dice that replaces numbers with words like "anus", "vulva", "penis" and "hands and fingers", The Times reports.
In the game, intended for secondary students, pupils are supposed to throw the dice twice and discuss the sexual acts relating to the body parts shown by the dice.
The trust received nearly £100,000 of government funding in 2017 towards the project, called Sexuality aGender.
The resource pack tells teachers: "Hold your nerve! Not all combinations will be easy to discuss and some might seem impossible.
"The aim is to get people talking and to limit assumptions about what kind of sex people have. Every combination is worthy of a conversation!"
The toolkit has been designed to help schools meet their obligations under the new Relationships and Sex Education curriculum that came into effect this month.
Jackie Doyle-Price, the Tory MP for Thurrock, expressed her "horror" at the resource.
Tanya Carter, a spokeswoman for Safe Schools Alliance, told the paper it "clearly breaches safeguarding" and would "prematurely sexualise" girls.