India's prime minister today signalled a huge push in nuclear power over the coming decades, using an untested technology based on nuclear waste and the radioactive element thorium.

Manmohan Singh, speaking at a conference of atomic scientists in Delhi, announced that 470,000MW of energy could come from Indian nuclear power stations by 2050 — more than 100 times the current output from India's current 17 reactors.

"This will sharply reduce our dependence on fossil fuels and will be a major contribution to global efforts to combat climate change," he said, adding that Asia was now seeing a huge spurt in nuclear plant building. The Indian plan, which relies on untested technology, was criticised by anti-nuclear campaigners as "a nightmare disguised as a dream".

The prime minister said a breakthrough deal with the US, sanctioned by the international community, had opened the door for the country to "think big" and meet the demands of its billion-strong population. He did not say how much the plans would cost, or how they would be paid for.

The intervention comes as talks in Bangkok aimed at resolving the impasse between developing and developed countries over a new climate change deal to replace the Kyoto protocol have stalled. India, one of the world's biggest emitters of greenhouse gases, has been dismayed that its pledges of action – including a dramatic expansion of nuclear power - have been met with inaction from richer nations.

The prime minister's statement also brings Delhi alongside Beijing which has long promoted atomic energy. India's plan would see it leapfrog its northern neighbour. At present China has 11 reactors in operation producing 8,000MW but has proposed that by 2020 this output be increased 10-fold. The UK, by contrast, has an installed capacity of around 12,000MW, much of which is due to go offline and be replaced by a new fleet of reactors in the next decade.

Nuclear power has been a contentious issue in India. Although the country has had a decades-old atomic programme, it was effectively blacklisted from global civilian nuclear trade after testing a nuclear device in 1974. That embargo was lifted in 2008 after negotations with Washington.

The result has been a rush to sign deals – both to supply uranium and to build reactors. France, Russia and the United States have all sought access to the booming Indian market.

India has an ambitious three-stage nuclear programme which it sees as a "silver bullet" to its dire energy shortage. At present 400m people cannot light their homes and the country imports 70% of its oil.

Delhi says that it will be able to surmount these considerable problems and generate clean green power with an atomic programme that "virtuously recycles" the plutonium waste that reactors produce. This radioactive isotope takes thousands of years to be rendered safe and dealing with it is the greatest challenge facing nuclear energy's proponents.

The Indian plan turns this waste into fuel. Using thorium, which is abundant in the country, combined with plutonium, the country aims to produce power and "breed" stockpiles of uranium.

It is a technology that no other country has mastered – and many have dropped – but India still has more than 2,000 scientists working on the technical problems.

Singh said the country had entered "stage two" of the programme and had completed a prototype breeder reactor in southern India.

However campaigners said "if climate change is the problem, nuclear power is not the answer". SP Udayakumar, convenor of India's Alliance for Anti-Nuclear Movements, questioned whether the technology India was pushing would ever be ready.

"The nuclear technology the prime minister talks about is not proven. If we start going ahead then the issue is the amount of carbon emitted by building, maintaining, operating and decommissioning nuclear plants means that (nuclear power) is a hugely polluting technology. If it does not work then we are left with waste that takes 24,000 years to become safe. It is a gamble we will pay for generations to come."