Coalition frontbencher Sophie Mirabella says she was in shock when GetUp! director Simon Sheikh collapsed next to her on live TV.

Ms Mirabella has received harsh reviews on Twitter after she appeared not to react when Mr Sheikh slumped forward and hit his head on the desk in the early stages of the ABC's Q&A last night.

At first it was not entirely clear if Mr Sheikh was playing a joke or picking something up.

But despite the fact that Ms Mirabella was sitting next to the GetUp! director, it was Climate Change Minister Greg Combet who first sounded the alarm.