Nine out of 10 people living in steel towns want Boris Johnson to deliver on a Brexit pledge to slash costs for the industry.
During the bitter 2016 referendum campaign, Mr Johnson tweeted: “Steelworkers should vote for Brexit. Mad that we can't cut steel energy costs because of EU rules.”
But six years on, the sector is battling sky-high power prices which threaten to cripple their industry.
A report by the Community steelworkers’ union, Our Steel Industry, found nine in 10 residents polled who live in steel communities in Wales, Yorkshire and Scotland, believe the Prime Minister should honour the commitment.
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The union urged the Government to announce support when Chancellor Rishi Sunak delivers his Spring Statement mini-Budget tomorrow.
Community researcher Anna Mowbray said: “We stand at a crossroads and the steel industry is under threat.
“The upcoming Budget presents a perfect opportunity for Boris Johnson ’s Government to deliver on promises to back British jobs and industry.
“The question is – will they?”
Britain’s £2.1billion steel industry directly employs 33,700 workers, with another 42,000 in supply chains.
But it is battling soaring energy costs and is under growing pressure to invest in green technologies to bolster the fight against climate change.
Today’s study, seen exclusively by the Mirror, reveals the extent to which families and businesses in steel communities rely on the sector.
Some 88% of steelworkers are the main breadwinner in their household, with “many supporting family members financially”, according to the report.
Fifty-two percent of those surveyed had relatives working in the steel industry or the supply chain.
The study says: “Steelworks are often at the social and economic core of towns, with a history of steel production providing a sense of local pride and togetherness.”
Ms Mowbray added: "The importance of the steel industry to our economy and national security is already very well known.
“We know that the steel industry is a crucial part of the supply chain for Britain’s defence sector, as well as for aerospace, manufacturing and other industries.
“What this report shows us is how important the steel industry is to families and communities across the country.”
A Government spokesman said: “We remain absolutely determined to secure a competitive future for our energy intensive industries, including the steel sector.
"We have in recent years provided them with extensive support, including more than £2bn to help with the costs of energy and to protect jobs.
“Volatile gas prices are a global issue, underscoring the importance of building a strong, home-grown renewable energy sector to further reduce our reliance on fossil fuels.”
The Mirror has been campaigning to Save Our Steel since 2015.