To add fuel to the fire
To make an argument or bad situation worse
e.g. There is a lot of anger about the government’s handling of Covid-19 but the publication of an email showing that a senior scientific advisor was told off after advising an earlier lockdown has added fuel to the fire.
Add fuel to the fire means to make a bad situation worse, to aggravate an already touchy situation, to make someone more angry or more annoyed. The idiom add fuel to the fire can be traced back to ancient Rome and The history of Titus Livius who lived around 1AD: “Not withstanding my remonstrance, you have added fuel to this fire, by sending to your army a youth who burns with an ambition of sovereignty…”