Why UK steel sector is alarmed by prospect of punitive tariffs from its biggest customer Why UK steel sector is alarmed by prospect of punitive tariffs from its biggest customer The EU shocked the UK steel industry on Tuesday with an announcement of 50% import tariffs – with no apparent carve-out for metal crossing the Channel. UK Steel, an industry lobby group, said the plan poses an “existential threat” to British steelmakers . Here’s what you need to know. The EU is the UK’s biggest customer: