Measures to protect British steelmakers are set to be cut from next month under plans presented to the Government.
A 107-page report to ministers recommends axing curbs on half of all imported steel products within weeks.
Experts fear a “catastrophic” flood of cheap foreign metal.
Protections were introduced by Brussels in 2018 when the UK was part of EU trade rules, in retaliation for Donald Trump's White House slapping tariffs on steel imports.
The EU measures carried on in Britain until January when the Brexit transition ended.
They were extended until June but the UK's Trade Remedies Investigations Directorate (TRID) has recommended safeguard measures are relaxed.
Furious unions and trade bosses blasted the move to slash defences – raising fears among producers of a flood of metal from abroad.
Community steelworkers’ union operations director Alasdair McDiarmid said: “This is the first test of the Government’s commitment to our steel industry post-Brexit and they’re failing it.
“The Government must reconsider this appalling decision which threatens jobs and puts the future of our industry at risk.
“This Government has had plenty of warm words for steelworkers but now it’s come to the crunch we’re being left exposed to a catastrophic surge of cheap foreign imports.
“Many steelworkers put their trust in the Tories but this announcement betrays them and makes a complete mockery of the levelling-up agenda.”
UK Steel director-general Gareth Stace said: “This formal proposal is a hammer blow to the UK steel sector and to the many thousands it employs.
“The recommendation by TRID to the Secretary of State to remove huge elements of the protection steel manufacturers require against import surges is madness and one that needs to be urgently rethought.”
Labour MP Stephen Kinnock, who chairs Westminster's All-Party Parliamentary Group on Steel and whose Aberavon constituency includes Britain's biggest plant, Port Talbot, said the “recommendation on safeguards really does add insult to injury for British steelworkers and their families and communities”.
He added: “This will be the first test of whether the interests of the UK manufacturing sector will be put at the heart of the Government's post-Brexit trade policy.
“If the Government fails to overturn this recommendation by TRID then it will become even clearer that the UK Government are not on the side of the British steel industry.”
The Mirror has been campaigning to Save Our Steel since 2015 when the industry was hammered by plan closures and thousands of job losses.
A Department for International Trade spokesman said: “We have a robust trade remedies framework via the TRID to protect UK producers from unfair trading practices and unforeseen surges in imports.
“This government supports free trade for British steel manufacturers.
“The Secretary of State has limited powers in relation to the TRA, and only has the choice under law to accept the TRA’s recommendation, or see safeguard measures expire at their end date.”
