1. say or do something to make a bad situation worse
his/her comments poured more gas on the fire
This expression adapts the fact that gas makes a fire burn more furiously, to express inflaming an already intense situation, or further upsetting a person or group who is/are already angry. It can often be done as an accident due to a slip of the tongue or an error of judgement, but sometimes is the result of a deliberate and calculated act. The expression is common in both a social and professional situation, and may sometimes be altered to 'add fuel to the fire,' particularly in the UK.