The prince devoted much of his speech to rainforests
Prince Charles has described the fight against global climate change as a war, with the Doomsday Clock "ticking ever closer to midnight".
In a speech to the European Parliament, he called for a solution to the loss of the world's tropical forests, to make them worth more alive than dead.
He said the crisis required the biggest public-private partnership ever seen.
The prince praised the European Commission's recent proposals to reduce greenhouse gases by 20% by 2020.
"Determined and principled leadership has never been more needed," he said. "Surely, this is just the moment in history for which the European Union was created?"
Prince Charles last addressed MEPs in 1992 with a speech that also dealt with the environment.
He told the parliament in Brussels on Thursday that no one could have predicted that climate change would become the leading concern of Europe's politicians and citizens.
The prince said it was time for a "genuine tripartite alliance", involving non-governmental organisations as well as the private and public sectors.
And he said it was crucial to work with pension funds and the insurance sector, to find out how they could make a difference.
Support for rainforests
But it was the issue of deforestation that the Prince of Wales devoted the main thrust of his speech.
The prince has met senior members of the European Commission
He said carbon emissions from the loss of tropical forests were comparable to those caused by electricity and heating.
Capital markets, he said, should be encouraged to transfer to countries which wanted to protect their forests "the huge sums" they needed.
He suggested that the emissions trading scheme that the EU has launched for European industry could be extended, so that emissions allowances could be auctioned to support rainforests.
The prince told his audience: "The lives of billions of people depend on your response and none of us will be forgiven by our children and grandchildren if we falter and fail."
Representatives from a number of the prince's charities have travelled with him, including the Prince's Trust, the Foundation for the Built Environment, the Rainforest Project, Prime Cymru and the Corporate Leaders Group on Climate Change (CLGCC).
Prince Charles will be followed to Brussels in the next fortnight by Gordon Brown.
The prime minister has not visited the commission since he took office and was criticised for arriving late to sign the Lisbon Treaty.
A commission official said the trip was "imminent" and it was "certainly being seen as an important signal".
Downing Street said the prime minister's trip to Brussels had been planned for the past two months.