Radical new climate change commitments will set the UK on course to cut carbon emissions by 78% by 2035, the UK government has announced.
Hitting the targets would require more electric cars, low-carbon heating, renewable electricity and, for many, cutting down on meat and dairy.
For the first time, climate law will be extended to cover international aviation and shipping.
But Labour said the government had to match "rhetoric with reality".
It urged Boris Johnson to treat "the climate emergency as the emergency it is" and show "greater ambition".
The prime minister's commitments, which are to become law, bring forward the current target for reducing carbon emissions by 15 years. This would be a world-leading position.
Homes will need to be much better insulated, and people will be encouraged to drive less and walk and cycle more. Aviation is likely to become more expensive for frequent fliers.
The government has accepted the advice of its independent Climate Change Committee (CCC) to adopt the emissions cut, which is based on 1990 levels.
The International Energy Agency (IEA) has predicted a major surge in CO2 emissions from energy this year, as the world rebounds from the pandemic.
The UK's new commitments come as US President Joe Biden prepares to stage a climate summit from Washington DC.
Environmentalists welcomed the government's move, but warned that ministers had consistently failed to achieve previous CCC-set targets.
And they insisted that Chancellor Rishi Sunak must show clearly how the transition is to be funded.
Tom Burke, who chairs the environmental think tank E3G, explained what policy changes were needed to achieve the goal: "The most important thing, I think, is for [the prime minister] to focus his policy around energy efficiency, around wind and solar, and around storage of electricity and the management of the grid," he said.
However, he told the BBC's Today programme: "At the moment, it's... a bit of a Boris blunderbuss and is a huge range of marginal things instead of a concentration of effort on those things that will deliver the most emissions reductions in the fastest time."
Leo Murray of the climate charity Possible called the announcement "fantastic", but added: "We're not on track to meet previous climate commitments and in many ways the government is still failing."
Mr Murray said ministers were "facing both directions at the same time", as they had scrapped the Green Homes Grant for insulating homes, had not stopped airport expansion and were "still pushing a £27bn roads budget".
The CCC report accepted by the government says low-carbon investment must scale up to £50bn a year in the UK. But it adds that in time fuel savings from more efficient equipment will cancel out investment costs.
The CCC believes around 1% of GDP - national wealth - would need to be spent on shifting away from fossil fuels over 30 years.
Its chairman, Lord Deben, said previously: "The implication of this path is clear: the utmost focus is required from government over the next 10 years.
"If policy is not scaled up across every sector, if business is not encouraged to invest, if the people of the UK are not engaged in this challenge - the UK will not deliver net zero by 2050. The 2020s must be the decisive decade of progress and action."
Ed Matthew, campaigns director of E3G, said: "Setting an ambitious emission reduction target would boost the UK's diplomatic drive to persuade other countries to set out ambitious targets of their own."
He added: "The UK now has the opportunity to spark a global green industrial revolution, but ultimately its credibility will rest on action."
Net zero means cutting emissions as far as possible, then balancing out any remaining releases by, for example, tree planting.
The government has adopted the new 2035 deadline for a 78% emissions cut because scientists say this is needed to keep the rise in global temperatures close to 1.5C above pre-industrial levels.
For Labour, shadow business secretary Ed Miliband said: "The character of this government on climate change is now clear: targets without delivery.
"So while any strengthening of our targets is the right thing to do, the government can't be trusted to match rhetoric with reality."
He added: "We need a government that treats the climate emergency as the emergency it is. That means greater ambition than this government matched with much more decisive action."
Green Party MP Caroline Lucas commented: "The most glaring problem [with the plan] is the government's failure to address what's driving the climate crisis: an outdated and exploitative economic system that treats our planet and natural world as peripheral to our lives and, worse, expendable.
"The Prime Minister needs to accompany stronger climate targets with an economic reset to put the health and well-being of people and planet above short-term profit and growth."
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