Ed Miliband is to say that the UK must stick to net zero targets to deliver jobs and growth, as speculation surrounds the energy secretary’s role under a new prime minister.

He will make the speech as data shows more than £100bn in green investment has been pledged by private sector companies in this parliament.

Miliband, who is due to address London Climate Action Week on Tuesday afternoon, is expected to say: “The UK’s clean economy is booming. Today we announce we’ve passed the incredibly significant milestone of over £100bn of private investment announced in clean energy since our government came to office. That means investment, jobs, growth.”

The speech comes as Miliband is tipped as a possible chancellor to succeed Rachel Reeves, who may follow Keir Starmer in stepping down. The net zero targets Miliband has championed have been cited as one of the reasons for the government’s unpopularity. Cabinet ministers, some trade unions and the rightwing media have regularly attacked Miliband, and claimed the push for net zero is a drag on the economy. Sharon Graham, Unite general secretary, said Miliband would be a “noose around the neck” of job creation if he became chancellor in a government led by Andy Burnham.

But experts told the Guardian that the new investment data, as well as previous findings by the Confederation of British Industry that the UK’s net zero economy has grown faster than the rest of the economy and generates higher paying jobs, suggested the contrary.

Offshore wind, solar power and the electricity grid make up the bulk of the planned investment, most of it between 2024 and 2031, which will go to all regions of the UK and comes from a mixture of UK companies and overseas sources including the EU and Japan.

Miliband is expected to say: “I’m proud to have led a pro-business, pro-growth department in these last two years. This achievement didn’t happen by accident, but because of clarity of mission, government investment and building not blocking. As we have shown in energy, progressive government in hard times requires partnership with business to secure economic growth, built on an active industrial strategy.”

He will add that a further boost is possible. “This is only the start of what we want to achieve. From nuclear to renewables, electrification to carbon capture and storage, clean energy can power growth and address the legacy of an economy that hasn’t worked for too many people in too many parts of Britain for too long.”

The future of the government’s net zero commitments is likely to be hotly contested. Starmer was a consistent supporter of renewable energy and net zero, but some of his core advisers, including his former chief of staff Morgan McSweeney, were cool on the policies and forced a watering down of key initiatives, such as by halving a planned £28bn public sector investment in low-carbon plans.

Andy Burnham, his most likely successor, was for years a champion of green initiatives such as offshore wind and renewable energy, but in recent months has tempered his tone with caution. Some of his supporters have tried to contrast his bid for “re-industrialisation” with the push for green energy and net zero, claiming they are opposed, and Burnham has said he was “open-minded” on whether to expand oil and gas drilling in the North Sea.

Economic experts told the Guardian that the best bet for boosting Britain’s economy would be to push for renewable energy and electrification, which would bring down energy prices and the cost of living, and remove the threat of damaging energy shocks like the Iran war and Ukraine war.

Bob Ward, policy director at the Grantham Research Institute of the London School of Economics, told the Guardian: “These (£100bn) figures demonstrate the potential scale of green investment, which can drive strong growth in the economy. Private investment is mobilised by clear and consistent policies, and a firm political commitment. It is essential that the next prime minister recognises the power of green investment, and creates an environment to foster it.”

Ed Matthew, UK director at the thinktank and consultancy E3G, said: “This is more powerful evidence that clean energy investment is the growth engine of the economy. It is also critical to weaning the UK off expensive fossil fuels which have cost Britain £183bn since the Russian invasion of Ukraine, and counting. Andy Burnham needs to seize this opportunity to slash bills and invest in the technologies of the future. The alternative is economic collapse.”

The investments include nearly £14bn in Scotland alone, and investments including £7.5bn from Japan’s Sumitomo conglomerate, £40bn from the National Grid for upgrades and £1.7bn in retrofitting social housing, from Barclays, NatWest and Lloyds banks and Rothesay, the pension insurer.