LONDON — The British government on Wednesday outlined legislation to reduce carbon emissions to net zero by 2050 in what it said would be a first for a major economy.

The target will be introduced in existing climate change laws through an accelerated mechanism known as a statutory instrument, the government said.

"As the first country to legislate for long-term climate targets, we can be truly proud of our record in tackling climate change," Prime Minister Theresa May was quoted as saying in a statement. She said Britain "must lead the world to a cleaner, greener form of growth".

"Standing by is not an option," she added. Britain's top advisory body on climate change this year said the target could be achieved within a budget of 1.0-2.0 per cent of gross domestic product by 2050.

But it added that it would require the rapid rollout of new policies such as making all new cars and vans electric by 2035 and quadrupling low-carbon electricity production.

The deadline would put the UK on track to fully meet its commitments under The Paris Agreement, under which countries have pledged to keep the global average temperature rise to well below 2 degrees Celsius.

If replicated across the world and coupled with near-term emissions reductions, there would be a greater than 50 per cent chance of limiting the temperature increases to just 1.5 degrees Celsius -- the "safe" upper limit identified by the UN's International Panel on Climate Change last October, the committee said.

Other EU countries have also pencilled in various emission reduction deadlines, although none have been adopted into law.

In France, the government introduced a bill in April setting a 2050 target date, while Norway is discussing 2030.

The world's net carbon emissions grew by an "unsustainable" rate of 2.0 per cent last year, according to a closely-watched review by energy giant BP published on Tuesday.

The review also found that global energy demand grew by 2.8 per cent, with the US recording the biggest increase of any country.

The UK government's move was quickly welcome by environmental campaigners from Greenpeace, which called it "a big moment for everyone in the climate movement".

"While the loopholes being woven into the legislation by the Treasury will need to be unpicked, and the date moved forward, this decision fires the starting gun for a fundamental transformation of our economy," the group's chief UK scientist Doug Parr said. — AFP