The next government must provide a “clear and funded” transition plan for workers in the offshore oil and gas industry, including the North Sea, green groups and unions have urged.

More than 60 climate organisations signed an open letter sent to all party leaders on Thursday based on a report backed by leading trade unions.

Signatories, which include Greenpeace, Oxfam and Friends of the Earth, are calling for a UK-wide industrial strategy, including substantial investment in domestic manufacturing and skills, expansion of publicly owned energy, and reorganising the tax system for public good.

The groups also urged the next government to expand sectoral collective bargaining across the energy industry and supply chain, and provide a jobs guarantee to ensure every oil and gas worker can find equivalent, alternative employment or funded retraining.

“The climate movement stands in solidarity with these workers and unions,” they wrote.

Mick Lynch, general secretary of the National Union of Rail, Maritime and Transport Workers (RMT) which backed the report, said the union will work with environmental groups and governments “to guarantee fair treatment, job security, and new opportunities for oil and gas workers”.

“We firmly believe that a just transition in the offshore energy sector is not just a necessity but a moral imperative to secure all our futures,” he said.

“As we move towards greener energy, it is crucial that the valuable skills and expertise of our members working in the oil and gas sector supply chain are not lost.”

The letter is also calling for a phase-out of oil and gas in the North Sea as a “crucial step” to meet the UK’s “binding climate commitments, address the UK’s historic role as a disproportionate producer of emissions, and prevent further devastating loss and damage”.

Elsewhere, the signatories said oil and gas industry jobs have halved in the last decade with around 227,000 lost since 2013, despite the government issuing hundreds of new drilling licences and energy firms recording record profits.

They also pointed to job losses already forecast at the Grangemouth oil refinery in Scotland and Port Talbot Steelworks in Wales.

The letter reads: “Industry bosses have been left to determine the terms of the decline, prioritising shareholder profits over affordable energy, green investment or job creation.

“The longer we wait to implement a worker-led just transition in the North Sea – and other high carbon industries – the worse off communities that rely on these industries will be.”

Analysis by the Trade Unions Congress suggests action to meet the UK’s climate commitments has the potential to create over a million good new jobs.

Mel Evans, Greenpeace UK climate team leader, said: “There is no such thing as climate justice without worker justice.

“We urgently need the next government to bring forward a bold green industrial strategy and transition plan to support workers into low-carbon jobs.”

A spokesperson for Unite the Union said it “welcomes support from the climate movement”.

“We are fully behind a transition to greener energy, but this must be a fair transition, one that has workers and communities at its heart,” they added.

Other signatories include Extinction Rebellion UK, Green New Deal Rising, Global Witness, Global Justice Now, #StopRosebank and Greener Jobs Alliance.

The report created in consultation with workers in the offshore oil and gas industry, was also backed by the Public and Commercial Services Union (PCS), Unite the Union Scotland and Unison Scotland.

Offshore Energies UK said the industry can support jobs, grow the economy and cut emissions by investing in £200 billion in energy projects in the UK through a transition backed by “homegrown companies”.

The trade body on Wednesday backed a declaration signed by five former cross-party ministers, including Amber Rudd and Brian Wilson, advocating the need for “critical” private investment by offshore energy companies, including oil and gas producers.

A spokesman said: “These investments matter to the 200,000 people whose jobs are supported by domestic offshore energy production and whose future relies on the national energy transition being a success.

“All parties have recognised the sheer scale of investment needed to reach net zero means private investment will be critical.

“As OEUK’s manifesto sets out, with a partnership approach and community engagement, the UK can deliver a transition which leaves no individual or community behind.”

A Conservative Party spokesman said: “These campaign groups highlight the danger that the Labour Party poses to our energy security and Britain’s 200,000 oil and gas workers through their ideological and ‘infeasible’ energy proposals that will shut down the North Sea oil and gas industry.

“Only Rishi Sunak and the Conservatives have a pragmatic plan that will bolster Britain’s energy security whilst delivering net zero without saddling families with the cost.”

Green Party co-leader Carla Denyer said: “We welcome this letter from leading climate organisations on a just transition, and the backing this has from unions.

“It is dangerous and reckless to continue extracting more oil and gas and elected Green MPs will push for phasing out fossil fuels.”