"The energy future we are facing today ... is doomed to failure," Claude Mandil, executive director of the energy adviser to 26 industrialised nations, told a news conference on Tuesday.
"We don't see how we can avoid [nuclear power] if we want a sustainable long-term future," Mandil said.
In its annual World Energy outlook, the IEA published a 596-page response to a G8 call for a sustainable energy blueprint.
The agency said unless leaders took action world demand for fossil fuels would rise by more than 50 per cent, along with carbon emissions.
By 2030, oil could soar to more than $130 a barrel if energy investment and government policies fall short, IEA said.
Energy conservation and investment in nuclear power could cut consumption by 10 per cent by 2030, equivalent to China's energy use today, the agency said.
"Clearly some countries that had said nuclear will not happen are now speaking again about nuclear,"
Claude Mandil, executive director of IEA
Carbon emissions would drop by 16 per cent - what the United States and Canada emit between them if more nuclear power stations are built, the agency said.
"The economics have moved in nuclear power's favour," the Paris-based IEA wrote in the report.
"Nuclear power offers considerable advantages in terms of avoiding greenhouse-gas emissions and of energy security."
It is the first time the IEA, set up after the 1973-74 Arab oil embargo, has backed nuclear power in such strong terms. This year's report devotes a whole chapter to nuclear energy.
At a G8 meeting in March, Sam Bodman, the US energy secretary, said he hoped for "a rebirth of the global nuclear industry".
Last week a British report by Nicholas Stern, the former World Bank chief economist, called for urgent action on climate change.
Supporters of nuclear power seized on the report, which warned of huge economic and environmental damage.
Sam Bodman, US energy
secretary, backs nuclear power
Even anti-nuclear Germany has suggested it may look again at its plan to phase out nuclear plants.
"Clearly some countries that had said nuclear will not happen are now speaking again about nuclear," Mandil said.
The World Nuclear Association [WNA] welcomed the IEA report.
"We are glad the IEA has given such a clear indication of nuclear power's ability to meet today's needs," a spokesman for the London-based organisation said.
"Nuclear is a proven, effective technology for providing stable electricity supplies on a large scale," the WNA said.
Nuclear plants provided just 15 per cent of the world's electricity last year.
Coal, a major source of greenhouse gases, and gas generate the vast bulk of the world's electricity.
The IEA conceded that the cost of building reactors - initial investment of up to $3.5 billion is needed - was a barrier.
Governments may need to be creative to attract private investment, it said.
It called for more efficient use of energy in light bulbs and cars, for instance.
Consumers will have to pay up initially, but those costs will be far exceeded by the saving, the IAE said.
"On average, an additional $1 invested in more efficient electrical equipment and appliances avoids more than $2 in investment in power generation, transmission and distribution infrastructure," Mandil said.
Without a radical change of behaviour, more than $20 trillion needs to be invested in new energy supplies by 2030, up from $17 trillion the IEA estimated a year ago, to meet demand, the report said.