The head of the largest coal workers' union has taken aim at both sides of the climate debate, saying the government needs to do more to reduce Australia's emissions but that should not include demands by the Greens to shut down the coal export industry.

In a speech to the Sydney Institute on Wednesday night, Tony Maher, the national president of the CFMEU, said "green activists'' were doing more harm than good to the climate change cause by targeting the export sector.