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 to low-income households over the next decade while wealthier households would receive interest-free loans for enhancements.
The party said loft insulation, enhanced double glazing and new heating systems would help cut energy use.
The Conservatives said the plan would “wreck the economy” and “put up bills”.
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 policy, called “Warm Homes for All”, would create 450,000 jobs involved in the installation of energy-saving measures and renewable and low-carbon technologies, the party said.
It said 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.
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.
Households which take out the loan would pay it back through savings on energy bills, Labour added.
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 in its latest pledge would be created, Labour said an estimated 250,000 skilled jobs would be in the construction industry in roles like insulation specialists, plasterers, carpenters and electricians.
It added its investment would generate another 200,000 jobs “across the economy”.
‘Homes of the future’
Shadow business secretary, Rebecca 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, build 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.