'The Green Party will pledge to invest £100bn a year in climate action for a decade if it gets into power.
Launching her campaign in Bristol, co-leader Sian Berry will say: "Some things are even bigger than Brexit. This must be the climate election."
The party says it will fund the pledge by borrowing £91.2bn a year, with a further £9bn from "tax changes" including a rise in corporation tax.
The Greens will also set out plans to make Britain carbon neutral by 2030.
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.
Political parties have begun to launch their election campaigns after the overnight dissolution of Parliament heralded the official start to the five-week campaign period.
Brexit is set to be a crucial issue when voters go to the polls on 12 December, with Prime Minister Boris Johnson insisting the UK will leave in January if he is returned to power.
However, some parties, including the Greens, are using their campaigns to draw attention to other issues.
Elsewhere in the election campaign on Wednesday:
- Boris Johnson is due to start the Conservative Party election campaign at a rally in the West Midlands and will say only his party can "get Brexit done"
- In a speech in Telford, Labour leader Jeremy Corbyn will say his government should be judged on the "real change" it delivers and "the concrete improvements it makes to the lives of millions"
At the Green Party election campaign launch, Ms Berry is due to say: "Let's be honest about the situation we're in. We know these are dark times. It's easy to fear the future.
"The threat of Brexit hangs over our heads, the climate emergency rages from the Amazon to the Arctic, and our fragile democracy is under attack.
"But despite all this, Greens don't fear the future.
"We welcome the future. Because we know that we stand at the threshold of what could be the most exciting and prosperous period of British history."
Read more: General election 2019: Green Party pledges £100bn a year for climate action