The Labour Party says it would be a disaster if a deal to tackle global warming was not reached at the United Nations climate summit in Peru.
The talks on slowing climate change are under threat after China clashed with the United States and led emerging nations to reject a compromise outline of an agreement.
China said the draft text put too much burden on poorer countries to limit greenhouse-gas emissions compared with the richer nations.
Labour Party leader Andrew Little said the talks were already in overtime because of the deadlock.
"The reality of climate change is that there is no turning back now, we have to do something and we have to better than what we've been doing, so an agreement at Lima is essential."
The delegates - from 190 nations - are seeking to agree on the foundation of a UN climate deal to be completed in Paris in December 2015.
Mr Little said an agreement in Lima would set things up nicely for next year's summit in Paris.