MILAN, June 14 (Reuters) - Former U.S. Vice President Al Gore denounced a deal by world leaders on curbing greenhouse gases as "a disgrace disguised as an achievement", saying on Thursday the agreement struck last week was insufficient.

The dedicated climate crusader, whose 2006 global warming documentary won an Oscar, said leaders at last week's G8 summit in Germany had not risen to the challenge to respond to what he calls a "planetary emergency".

G8 leaders agreed to pursue "substantial" reductions in greenhouse gas emissions, stopping short of German Chancellor Angela Merkel's hopes for concrete numerical commitments on emission reductions, including her key aim to cut gases by 50 percent by 2050.

They said they would negotiate a new global climate pact that would extend and broaden the Kyoto Protocol beyond 2012.

"It was a disgrace disguised as an achievement," Gore said at an event in Milan, where he praised Merkel for her efforts.

"The eight most powerful nations gathered and were unable to do anything except to say 'We had good conversations and we agreed that we will have more conversations, and we will even have conversations about the possibility of doing something in the future on a voluntary basis perhaps.'"

The former U.S. Democratic presidential candidate is spearheading efforts to get the world of pop music to back his crusade with the Live Earth concerts on July 7, which will be held in numerous cities around the world.

Gore served as Democrat President Bill Clinton's vice president and narrowly lost the 2000 election to George W. Bush.

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