A Liberal Democrat government would spend £100bn tackling the effects of climate change and protecting the environment, the party’s finance spokesman is set to announce.
In a speech on Friday, Sir Ed Davey will say the five-year investment would “jump-start” efforts to combat the “climate emergency”.
The pledge would be funded through borrowing and tax changes.
The Conservatives and Labour both have targets to reduce carbon emissions.
Sir Ed, who served as secretary of state for energy and climate change in the coalition government, is expected to say that “across a five-year Parliament, Liberal Democrats would spend and invest an extra £100bn of public finance on climate action and environmental preservation”.
“This includes a new £10bn ‘renewable power fund’ to leverage in over £100bn of extra private climate investment,” he will add in the speech in Leeds.
“This will fast-track deployment of clean energy, to make Britain not just the world leader in offshore wind, but also the global number one in tidal power too.
“And we will invest £15bn more to make every building in the country greener, with an emergency ten-year programme to save energy, end fuel poverty and cut heating bills.”
The party said the policy would be funded through £85bn of borrowing and £15bn raised through tax changes, which will be detailed in its manifesto.
Sir Ed is also expected to attack the “fantasy economics” of Prime Minister Boris Johnson and Labour leader Jeremy Corbyn.
He will say that, so far, spending plans unveiled by the Conservatives and Labour represent a “debate between fantasies”.
“Fantasies born of nostalgia for a British Imperial past. Competing with fantasies from a failed 1970s ideology.”
The deputy Lib Dem leader will also champion a so-called “Remain bonus” of £50bn to fund schools and tackle inequality.
BBC Reality Check correspondent Chris Morris said the vast majority of forecasts do expect the economy would be bigger if the UK were to stay in the EU.
But he added the size of that “bonus” cannot be predicted with any certainty, and £50bn was not a hugely significant amount in terms of overall government expenditure.
The Lib Dem climate pledge follows the Green Party’s promise to appoint a “carbon chancellor” to allocate £100bn per year towards climate change.
Labour, the Lib Dems, the Scottish National Party and the Green Party have called for a live TV debate on climate change before the 12 December election.