The long-awaited review of the economic impact of rising world temperatures by former World Bank chief economist Sir Nicholas Stern warned that time was running out for effective action.
While the Prime Minister acknowledged that Britain needed to be "bolder" in the measures it adopted, he stressed the problem could only be tackled through coordinated international action.
"What is not in doubt is that the scientific evidence of global warming caused by greenhouse gas emissions is now overwhelming," he said at the report's launch at the Royal Society in London.
"It is not in doubt that if the science is right, the consequences for our planet are literally disastrous."
"This disaster is not set to happen in some science fiction future many years ahead, but in our lifetime.
"Unless we act now... these consequences, disastrous as they are, will be irreversible.
"There is nothing more serious, more urgent, more demanding of leadership - here, of course, but most importantly in the global community."
Sir Nicholas insisted that his review was "essentially optimistic".
While it put the cost of unchecked climate change at between 5 per cent and 20 per cent of global output, it showed that carbon emissions could be stabilised for around 1 per cent of output - provided action was not delayed.
"There is still time to avoid the worst impacts of climate change, if we act now and we act internationally," he said.
"But the task is urgent. Delaying action, even by a decade or two, will take us into dangerous territory. We must not let this window of opportunity (pass)."
The report set out a three-pronged strategy based on carbon pricing, support for the development of low-carbon technologies, and a drive to "inform, educate and persuade" individuals about what they do.
Its recommendations are based on stabilising C02 levels in the atmosphere at between 450 and 550 parts per million (ppm) - which would still require a cut of at least 25 per cent in global emissions.
It accepts that even with a very strong expansion of renewable energy sources, fossil fuels could still account for over half of global energy supply by 2050.
Therefore extensive carbon capture and storage will be necessary, while reductions in non-energy emissions - such as industry, agriculture and deforestation were also essential.
The Chancellor Gordon Brown, who commissioned Sir Nicholas's report, called for a long-term framework of a worldwide carbon market, leading to "a low-carbon global economy".
He set out proposals for a new European-wide emissions reduction target of 30 per cent by 2020, and at least 60 per cent by 2050 - eventually to be extended worldwide.
"Building a low-carbon economy in Britain and across the world means higher productivity from increased energy efficiency, it means new markets, jobs and exports from environmental technologies and products," he said.
"As the international community begins to build the long-term framework that I am describing, as the European trading scheme expands into a global carbon market, a new low-carbon global economy will take shape."
Sir Nicholas's report said that an expansion and linking up of carbon emissions trading schemes around the world should form a key element of any future international framework.
It emphasised the importance of international cooperation on developing new, low-carbon technologies, both through informal coordination as well as through formal agreements.
With the loss of natural forests around the world contributing more to global emissions than the entire transport sector, it said that curbing deforestation offered a highly cost-effective way to reduce emissions.
The report also stressed that, with the poorest countries of the world most vulnerable to the effects of climate change, it was essential that the issue was fully integrated into international aid programmes.
The Prime Minister's official spokesman said Britain only accounted for 2 per cent of the world's emissions.
"This is an issue with which primarily the focus has to be on global solutions to a global problem."
He stressed that the Stern Report was making the economic case for tackling climate change. The number of jobs in the UK that were related to developing green technologies had risen sharply.
"Green technology equals jobs," he said.
The spokesman added: "What we're now after is international agreement, firstly on stabilising emissions and then on creating a series of mechanisms such as we agreed, for instance, with the Governor of California when we were there - a link between here and California.
"We want that to apply to Europe as well."
The spokesman said Mr Blair had repeatedly emphasised the link between climate change and energy security, and now appeared to have won that argument.
He refused to give details of the Climate Change Bill expected to be announced by Environment Secretary David Miliband in the Commons later.
However, he did indicate that there would be problems with setting annual targets for reducing emissions, because of the way the economic cycle worked and variations in the weather from year-to-year.
"The issue is not targets," he said. "The issue is whether they should be annual."
Sir Nicholas's report was welcomed both by environmental campaigners and business.
Charlie Kronick of Greenpeace said that the report showed that it was up to the current generation to defeat climate change.
"We always knew that the scientific and moral case for action was overwhelming, but this report is the final piece in the jigsaw," he said.
"There are no more excuses left, no more smokescreens to hide behind, now everybody has to back action to slash emissions, regardless of party or ideology."
CBI director general Richard Lambert said a global system of emissions trading was now urgently needed as a "nucleus" for effective action
"Provided we act with sufficient speed, we will not have to make a choice between averting climate change and promoting growth and investment," he said.
"This will require an international partnership between the public and private sectors, working alongside civil society and with individuals.
"It will be one of the great challenges of the 21st century, and the difference between our success or failure will affect the lives of generations to come."
Oxfam's director of campaigns and policy, Phil Bloomer, said that the urgency of the report had to be matched by immediate Government action.
"For hundreds of millions of people living under the constant threat of drought or flood, urgent action on climate change is vital," he said.
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