In recent years, Britain has been busy setting up the scaffolding of the country’s future low-carbon economy. But beyond the Westminster pledges and white papers lies a very practical challenge: where are the workers who will bring the government’s green agenda to life?

Britain’s greatest industrial transformation since the Industrial Revolution will require a change on a similar scale: hundreds of thousands of jobs are expected to be created by the needs of a low-carbon economy. There are thousands of miles of cables to add to the national grid, electric car battery factories to build, heat pumps to install, and rising demand for wind and solar farms. Experts warn of a “critical shortage” of certified welders and electrical engineers, and fear that the government may have left it too late.

Ed Miliband, the shadow energy secretary, says Britain is facing a once-in-a-generation opportunity to rebuild the economy. But the prime minister is “asleep at the wheel”, he says, while the Tories are “happy to let jobs and wealth that could rebuild Britain go overseas instead”.

“Britain’s joiners, welders, engineers, technicians and construction workers are the people who are going to deliver a green future for this country,” Miliband says. “Yet under the Conservatives, far too many good jobs have gone overseas, as other countries get ahead in sectors like steel, electric car production, and clean energy.”

Analysts at the IPPR, a left-leaning thinktank, believe that as many as 1.6m new jobs could be created in the transition to a green economy. The looming skills gap is both a threat to the UK’s net zero ambitions and a big economic opportunity, according to Luke Murphy, an associate director at the IPPR.

“We’ve done exceptionally well on the rollout of offshore wind, for example,” he says. “But we’ve failed to capture the economic opportunity the way other countries have.”

The IPPR has found that the UK employs fewer people in renewable energy as a proportion of its working-age population than most other European countries. In wind, if the UK was performing as well as Denmark – home to offshore giant Ørsted – it could secure an additional 98,000 jobs, it believes. “Unless we have the industrial strategy and necessary skills in place to take advantage of the green transition, we risk missing our net zero targets, and failing to take advantage of the opportunity that lies ahead of us,” Murphy says. “The task ahead requires not only a net zero strategy but an industrial strategy alongside it.”

Forecasts for the number of jobs required to realise Britain’s low-carbon ambitions vary. The government’s official climate advisers at the Committee on Climate Change have estimated that between 135,000 and 725,000 net new jobs could be created by 2030 in low-carbon sectors such as generating renewable energy, upgrading buildings and manufacturing electric vehicles.

Welders and electrical engineers are in critically short supply, according to Phil Beach, the chief executive of Energy and Utility Skills, a trade association. He estimates that there are only “several hundred” certified welders currently in the UK but the country will need “several thousands” to get to net zero. There are similar concerns for the number of certified electrical engineers, who will be needed across the energy system.

“We need to train as many electricians as we can,” Beach says. “This decade we’re expected to lose 20% through retirements – so we’re already looking to find 275,000 roles to be filled this decade. “It can take two to three years to become fully qualified, so we’re facing a critical shortage.”

Ministers hope to increase Britain’s offshore wind capacity to 50 gigawatts by 2030, up from just over 10GW at present, and solar capacity fivefold by 2035. They also hope to build 24GW of nuclear power capacity by 2050, from just under 7GW at present. As a result, more than 600,000km of electric lines will need to be added or upgraded across the UK to connect these projects to the grid.

Meanwhile, in homes across the country, up to 600,000 heat pumps could replace gas boilers every year under government targets, and electric vehicle charging points are expected to appear along residential streets and motorways.

Each element of this plan requires thousands of skilled workers. There is a “massive shortage” of qualified heat pump engineers, according to Nesta, an innovation charity. The current number of accredited heat pump engineers is estimated to be about 3,000 but Britain will need at least 27,000 by 2028 to meet the government’s target.