Pop star Lily Allen's BBC chatshow has come under fire after the star previewed a controversial video clip to viewers - featuring a teacher having his trousers pulled down in front of a class of students. The Smile star showed the footage on her show Lily Allen And Friends on Tuesday (18Mar08) night as part of the programme's 'funny Internet clips' section. Introducing the video, the singer told the audience, "Now it's my favourite, it's 'kegging' a teacher - pulling someone's trousers down in public when they least expect it. It's very childish, but very funny." But Allen has come under scrutiny for choosing to show the clip - with Britain's Teacher's Union branding the stunt "completely and utterly irresponsible". A representative for the Association of Teachers and Lecturers says, "If she doesn't understand the responsibility of what she is doing in the media world, then she should not be allowed to do that."