Al Gore, the high-profile climate change campaigner and former U.S. vice president, said Japan would abdicate leadership responsibilities as a top global economy if it sustains its support for coal.

Speaking Thursday on the sidelines of an event hosted by environmentalists in Tokyo, Gore added his voice to criticism of the pro-coal policies of Japan, which was blocked from speaking at last month's United Nations climate summit in New York.

"If they build as many new coal plants as some now propose, and subsidize as many new coal plants in other countries as they now have planned, of course that would be a massive policy failure," Gore said.