The Green Party says it will appoint a "carbon chancellor" to allocate the £100bn per year they have pledged for tackling the "climate emergency" if they are elected to power.
Co-leader Jonathan Bartley said the chancellor will lead a new department and issue an annual carbon budget.
The party will fund the £100bn pledge mostly through borrowing.
The independent Institute for Fiscal Studies says this will take government borrowing to £140bn.
Meanwhile, Scotland's First Minister Nicola Sturgeon will unveil a "Green Energy Deal" to support investment into energy schemes.
The SNP leader will say that Westminster needs to "get its act together" on tackling long-term energy challenges.
The Green Party for England and Wales says the new carbon chancellor role will head up the Department for the Green New Deal and the Treasury will become a new Department for Economic Transformation if they are elected on 12 December.
They have pledged that £100bn a year will be spent on tackling the "climate emergency" for a decade - worth £1tn over 10 years - and the party aims to make Britain carbon neutral by 2030.
The £100bn pledge will be funded by borrowing £91.2bn a year, with an extra £9bn from "tax changes".
In other election developments:
- Tory Party leader Boris Johnson will say in his first major election speech the UK cannot afford to "squander" more time deciding whether and how to leave the EU
- Labour is promising to outspend the Conservatives on the NHS in England
- The Lib Dems are proposing a £500m investment in youth services aimed at combating knife crime
- Former Tory rebel David Gauke is standing as an independent candidate - on a second EU referendum platform - in South West Hertfordshire
- Nigel Farage has been warned he has 48 hours to "save Brexit" by long-time ally and financial backer Arron Banks, who called on him to stand down more candidates
Explaining the new role, Green Party co-leader Mr Bartley said they needed to "fundamentally change the way government works" if they were going to have "any hope of tackling the climate emergency".
"Every sector of the economy needs to decarbonise if we are to become carbon neutral by 2030," he said.
"Only the Green Party has the bold vision and practical solutions to make our economic system work for the people and the planet.
"A carbon chancellor in 11 Downing Street will mean the prime minister can't even walk out of the front door without thinking about the climate emergency."
The government has already committed to cut carbon emissions to net zero by 2050, a move announced by former Prime Minister Theresa May before she left office earlier this year.
Reality Check: Where would the £100bn come from?
By Tom Edgington, BBC Reality Check
The Greens believe a large public investment, worth £1tn over 10 years, is essential to fight climate change and make Britain fossil fuel free by 2030.
They say £91.2bn a year would come from borrowing - this would represent a huge hike on current levels
The party justifies this by saying that rates are at "unprecedented historical lows".