Campaigners have warned that Brexit has left the UK “much more exposed” after reports that the EU is preparing a new 50% tariff on steel imports.

The move has been described as “perhaps the biggest crisis” the UK steel industry has ever faced – and called an “existential threat” by the Community Union representing steelworkers.

The quota of steel imports into the European trading bloc – which is the UK’s top export destination for steel – are set to be cut almost in half to 18.3 million tonnes a year.

From early next year, imports above that level will be subject to the new 50% tariffs – once the measure is approved by members and the EU Parliament.

It comes after the European Commission came under pressure from some member states as their steel industries were struggling to compete with cheap imports, including from China, the BBC reported. The decision is also seen as a response to the similar moves from the US.

Naomi Smith, Chief Executive of Best for Britain, said:

“This troubling development is yet another demonstration of the mounting cost of Brexit and Nigel Farage will have to explain to the steel workers he pretends to champion, how leaving the EU has benefitted them.

“Outside the EU we are much more exposed and this, coupled with the expectation that Trump will force the NHS to pay more to US pharma companies, is catastrophic news ahead of the Budget.”