The chancellor has announced measures aimed at cutting the UK's greenhouse gas emissions - as part of £1bn spending to tackle climate change.
The Budget commits the UK to cut CO2 emissions by 34% by 2020.
Industry has pushed for the measures, saying it will allow them to invest in "greener" technologies, but scientists say the targets do not go far enough.
An extra £525m was also pledged in the next two years to help get off-shore wind farm projects under way.
This would providing enough power for three million homes, Alistair Darling said.
"On the back of the discovery of oil and gas in the North Sea, we became a world leader in that field. I am determined we will replicate those successes across renewable energy and low carbon energy," he added.
But businesses complained that this could put UK competitiveness at risk unless other big nations cut emissions too, so they recommended a 34% unilateral cut by 2020 pending a global agreement.
Environmental group Friends of the Earth said the emissions cuts were far too weak to allow the UK to "play its part in avoiding dangerous climate change".
"Setting the first ever carbon budgets is a ground-breaking step - but the government has ignored the latest advice from leading climate scientists and set targets that are completely inadequate," said the group's executive director, Andy Atkins, who added a 42% cut by 2020 was the minimum needed.
Alistair Darling on 'the world's first ever carbon budget'
The New Economics Foundation dismissed the Budget as being "more beige than green".
Christian Aid's climate policy expert Dr Alison Doig said the UK and other industrialised nations needed to urgently commit to deeper emissions cuts ahead of a climate change summit in Copenhagen in December.
"Cutting emissions by 34% by 2020 will fail to prevent dangerous global warming from devastating the lives of people in developing countries, who are least responsible for this crisis," she said.
"This is not leadership. It is not even adequate."
"Green technology" would be a great growth sector in the world economy, Mr Darling said.
"These efforts also have the potential to create thousands of hi-tech businesses and hundreds of thousands of high-skilled jobs," he added.
The chancellor also announced investment in carbon capture and storage - a way of reducing carbon emissions while still using fossil fuels such as coal.
The UK would fund at least two - and up to four - demonstration projects instead of one, Mr Darling added.
The offer of taxpayer money to support carbon capture and storage would put pressure on government to make sure such projects were delivered on time to the benefit of the UK consumer, said Jim Fitzgerald, a director at Ernst & Young.
The move added to the prospect of creating UK jobs, but delays in selecting the projects to receive the funding would give other countries a head start, he warned.
"Strong competition from countries such as Germany the US and China mean that the UK government risks losing the race to win green jobs and investment from CCS technology."
The chancellors budget also contained a promise of £435m for insulation improvement and better central heating for homes, businesses and public buildings.
New power plants which improve their efficiency by using the heat produced in the generation of power would be exempt from the climate change levy from 2013.
Mr Darling said that would save the firms more than £2.5bn which they could then invest in energy generation.
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