Labour is pledging to cut UK carbon emissions by 10% through the largest home improvement programme for decades.
A Labour government would fund £60bn of energy-saving upgrades, such as loft insulation, enhanced double glazing and new heating systems, by 2030.
Launching the policy on Sunday, Jeremy Corbyn said it “will create a sustainable energy network”, adding: “We cannot go on polluting our planet.”
The Conservatives said the plan would “wreck the economy” and “put up bills”.
Speaking about the policy – called “Warm Homes for All” – in south-west London, Mr Corbyn said that climate change would be a major part of the party’s election campaign.
“We cannot go on standing by while climate warming increases,” the Labour leader said.
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Labour says low-income households will receive a grant to carry out the work on their homes, while wealthier households would receive interest-free loans for enhancements.
Households which take out the loan would pay it back through savings on energy bills, the party added.
Labour expects the project to cost £250bn – an average of £9,300 per home – but only £60bn would come as a cost to central government, it says.
Speaking on Sky’s Sophy Ridge on Sunday, shadow business secretary Rebecca Long-Bailey said the £60bn would come from its £250bn National Transformation Fund. Interest-free loans would make up the remaining cost of the policy, she said.
She added: “Overall, we’re looking at generating more jobs and supporting businesses through the economy, so that by 2030 the increased tax-take more than recoups that £60bn outlay.”
A spokesperson for the Tories said, while tackling climate change was vital, “independent experts and even Labour’s own unions say their promises don’t stack up”.
Labour says its proposals would create 450,000 jobs involved in the installation of energy-saving measures and renewable and low-carbon technologies.
Almost all of the UK’s 27 million homes would benefit from the pledge, either through a grant to fund works in full, or an interest-free loan, it said.
Interest-free loans to improve the energy efficiency of homes are already available in Scotland, where the issue is devolved to the Scottish government.
A Labour spokeswoman told the BBC the party would make every effort to work with devolved powers to implement the plan across the whole of the UK.
The party said the plan would cut carbon emissions by 10% by the year 2030 and reduce energy bills for 9.6 million low-income households by an average of £417 a year.
The policy echoes previous announcements from Labour, including a pledge last year to create over 400,000 skilled jobs through investment in renewable energy and making homes energy efficient.
Over the past year or so the Labour Party has come out with a series of proposals to improve the energy efficiency of British homes.
This plan is far larger – and also far more expensive. It involves, over the next decade, spending £250bn to fit every UK house with double-glazing and loft insulation, heat pumps and solar panels.
Households with low incomes would not pay anything. Wealthier ones would get interest free loans. Everyone, it’s said, would benefit from lower bills and the UK as a whole would see its carbon emissions fall.
Much of the country’s housing stock is relatively old and upgrading it is seen as essential to meeting our targets on climate change. But critics will say Labour’s scheme lacks detail and that the estimates for the costs are unrealistic.
The initiative comes a day after the Conservatives called a halt to fracking, a sign that the political parties sense the environment has become a key issue for voters.
Outlining where the additional jobs would be created, Labour said an estimated 250,000 skilled jobs would be in the construction industry – roles like insulation specialists, plasterers, carpenters and electricians.
In addition, it claimed the investment would generate another 200,000 jobs “across the economy”.
‘Homes of the future’
Ms Long-Bailey said the pledge was “one of the greatest investment projects since we rebuilt Britain’s housing after the Second World War”.
She said: “Labour will offer every household in the UK the chance to bring the future into their homes – upgrading the fabric of their homes with insulation and cutting edge heating systems – tackling both climate change and extortionate bills.”
A Conservative Party spokesperson said: “The reality is that Jeremy Corbyn’s plans would wreck the economy, putting up bills for hardworking families – and preventing any real progress on climate change.
“Only Boris Johnson and the Conservatives have a proper plan to continue reducing carbon emissions faster than any other G20 country, building on the 400,000 low-carbon jobs we’ve already created, while keeping bills low.”
On Saturday, Labour said it would ensure all new-build homes in Britain were “zero carbon” within three years.
It said a Labour government would introduce “tough” standards on new builds which would see homes fitted with solar panels and a ban on gas boilers.
The party has previously said it intends to bring energy supply networks into public ownership.
It comes as the government called a halt to shale gas extraction – commonly known as fracking – in England amid fears about earthquakes.
Labour, the Liberal Democrats and the Green Party want to ban fracking permanently.