The GMB union said its research suggests that between 1981 and 2021 almost 80 per cent of jobs in the entire steel sector have gone.
Workers from across the country marched from Trafalgar Square to Parliament Square calling for a "proper industrial strategy" and relief from the energy costs unions say are crippling the steel sector.
Charlotte Childs, GMB national officer, said: "Under this government's watch, the UK's proud steel industry is being allowed to wither and die. Almost 150,000 jobs have gone – close to 80 per cent of the entire steel workforce.
"A lack of industrial strategy and no support for crippling energy costs have left the industry at risk of 'steel dumping' from overseas. We need action now or the industry as we know it will cease to exist."
Image credit: James Manning/PA Wire
Roy Rickhuss, general secretary of Community, said: "Britain needs its steel industry, our country is made from it – the roads we drive, the bridges we cross, the hospitals that heal us and the schools our children learn in.
"But the UK government must decide whether it wants a steel industry in this country. In the absence of government backing, we face Britain's proud history of steelmaking coming to an end.
"Our steel industry cannot survive if we continue to pay far more for energy than our EU competitors and it cannot decarbonise if the government doesn't support the transition toward net zero.
"Steelworkers don't ask for handouts – simply the chance to compete on a level playing field and to protect an industry of crucial national importance."
A Department for Business and Trade spokesman said: "This government believes that steel plays a vital role in the UK economy, supporting local jobs and economic growth.
"We introduced the British Industry Supercharger to make our steel industry more competitive by bringing down energy prices and protecting the UK steel industry from unfair trading practices.
"We are working closely with the sector to secure a sustainable, decarbonised and competitive future for steel."
Image credit: Aaron Chown/PA Wire
Unite union general secretary Sharon Graham said at the protest: "We stand on the very precipice for Britain's steel industry. It's time our politicians stepped up to the plate and took action to save our most vital of industries. How can it be that Belgium produces more steel than Britain?
"There has been criminal negligence in flogging off the industry in a privatisation that has proved calamitous – a private equity scam that didn't work.
"Of course steel is a foundation industry – over 25 per cent of Britain's GDP is delivered by industries dependent on steel. Are we now going to stand by and watch it collapse?
"That would be a catastrophe for British manufacturing and looming jobs losses of 40,000 in the industry and more in related industries and supply chains. But steel is also fundamental to the security of our country. What are we going to do if steel goes bust – import it from the Chinese?
"Every British major infrastructure project should be legally committed to using British steel on their projects. Unite research suggests if that one thing was done today it would guarantee an increase in steel production worth £8 billion and create 3,000 jobs.
"There is a green revolution beckoning in steel where blast furnaces must be replaced by electric arc furnaces to decarbonise production. Britain could be a world leader in that transformation."
Earlier this week, trade body UK Steel warned that EU carbon costs could 'crush' the UK steel market and almost 23 million tonnes of non-EU steel could flood the UK market without government action.
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