Critics said that parents would be ‘horrified’ by the possible introduction of pornography into classroom lessons.

Under a section titled ‘We want teachers to know’, the guide includes advice that ‘that porn is hugely diverse – it’s not necessarily all bad’.

The ‘wish list’ section, which aims to create the ‘ideal environment’ for teaching about sexual issues, also advises teachers to ‘speak frankly and confidently’ about pornography.

In a model lesson plan, it is suggested that children are told about the differences between what is ‘real’ and ‘unreal’ in pornography, using a device known as the ‘planet porn game’.