Unions have revealed details of a plan aimed at safeguarding the future of the UK’s biggest steel plant without the loss of thousands of jobs.

Community and the GMB said their proposal would secure a just transition for the workforce at Port Talbot in South Wales and across owner Tata Steel UK, and deliver on the country’s climate responsibilities.

The unions have condemned plans to produce “green” steel at the site with the potential loss of thousands of jobs, saying they are “seriously concerned” about the proposal to build a single electric arc furnace (EAF).

They said their two-phase plan would protect more than 2,300 jobs over a decade and see no compulsory redundancies at Port Talbot.

Community general secretary Roy Rickhuss said: “The multi-union plan can safeguard the future of Port Talbot steel-making and protect all the downstream plants, and crucially it can be delivered with no compulsory redundancies.

“It is a serious and credible plan developed with the support of the respected industry experts Syndex, who have had access to the company’s confidential information and who have in-depth knowledge of Tata Steel UK, having worked with us since 2014.

“Our alternative is ready to go and we call on all stakeholders to get on board and back the plan, back our industry and back our steelworkers.”

GMB general secretary Gary Smith said: “Port Talbot workers deserve a decarbonisation plan that protects the future of UK steel while safeguarding jobs.

“The multi-union plan offers a credible path to this future.

“It’s feasible, open to proper scrutiny and crucially avoids any non-compulsory redundancies.

“It’s the plan Port Talbot workers want – now unions, Tata and the Government need to make sure it’s implemented.”

Sarah Jones, shadow minister for industry and decarbonisation, said: “It is welcome to see Tata engaging with a multi-union process around an alternative proposal for Tata Steel UK.

“There can be no route to green steel without proper engagement with the workforce to ensure we do not simply ship our emissions and jobs overseas.

“Labour is hopeful all parties can reach a solution in partnership with workers and industry, investing in a range of technologies to decarbonise steel and build the jobs and opportunities for the future of the UK steel industry.”

Stephen Kinnock, Labour MP for Aberavon, said: “This detailed, serious, robust and compelling plan for the future of the Port Talbot steelworks has my full and unequivocal support.

“It’s the only realistic route to retaining our customer base, and it’s also the only credible pathway to a strong, competitive and profitable future for steel-making in Port Talbot and throughout the downstream plants across Wales and the UK.”

The Unite union has put forward its own proposals, arguing there is no need for any job losses at Port Talbot.

A Tata Steel spokesperson said: “Tata Steel has an agreed and well-established multi-union Information & Consultation arrangement for matters potentially affecting the company – The UK Steel Committee.

“Senior leaders from Tata Steel met with the UK Steel Committee and their advisers on November 17 to start discussions on their proposals. We agreed to further detailed conversations on specific items within their proposal and these discussions are ongoing.”