Leaving the European Union without a deal would put Sheffield steel jobs at ‘immediate’ risk.
UK Steel said that all steel exports beyond a certain ‘quota’ level would be hit with 25 per cent tariffs, which could cost the country’s steel producers £1.2 million a day.
This was a cost ‘neither UK steel producers nor our customers would be able to shoulder’, UK Steel said.
John Healey, MP for Wentworth and Dearne, said he understood half of the product of South Yorkshire Speciality Steels’ plants, which are run by Liberty UK, was exported to the EU.
“The public rightly expected an orderly Brexit on March 29, as the Government had told us for over two years,” he said.
“But they’ve failed to negotiate a decent Brexit deal, so we now face national humiliation and chaos.
“This internal briefing about what will happen at the end of next week exposes the real world results of a crash-out Brexit.
“The impact would be immediate, with local jobs, wages and businesses at direct risk.
“I’ve spoken with the business secretary and told him to step in and fix this big threat to South Yorkshire steel.”
Liberty House Group announced bought Tata’s plants in Stocksbridge and Rotherham, which employ around 1,700 workers, in 2017.
Theresa May has written to the European Union to request a further delay to Brexit until June 30.
The UK is currently due to leave the EU on April 12 and, as yet, no withdrawal deal has been approved by MPs.
The prime minister has proposed that if UK MPs approve a deal in time, the UK should be able to leave before European Parliamentary elections on May 23.
But she said the UK would prepare to field candidates in those elections, in case they do not reach agreement.