In his report handed to the Government on Tuesday, Professor Garnaut promoted the idea of reducing conventional livestock numbers by as much as 30pc in order to accomodate an expansion in the kangaroo population to 240 million head.

"Australian marsupials emit negligible amounts of methane from enteric fermentation," he said.

"This could be a source of international comparative advantage for Australia in livestock production.

"For most of Australia's human history – around 60,000 years – kangaroo was the main source of meat. It could again become important."

But the idea has been condemned and ridiculed by rural leaders, with Opposition agriculture spokesman, John Cobb, saying the "proposal would be laughable if not so serious".

"The cost to the nation would be terrifying," Mr Cobb said.

"The cattle and sheep industries are worth billions and billions of dollars and are the backbone of country Australia.

"Perhaps the most extraordinary aspect of this proposal is that the very same champions of an emissions trading scheme, the environmental and green-shoe brigade, have been fighting to destroy the kangaroo industry in Australia for the last 30 years and have in the main been successful."

Cattle Council president Bill Bray said the idea was "simply not an option".

"This is a diversion from realistic ways of reducing emissions," Mr Bray said.

"Of course we are not opposed to kangaroo production; however, our global customers collectively purchase around $120 million per week worth of beef and beef products.

"Any carbon 'leakage' from Australia toward countries that are not investing in research and development and improving productivity will ultimately detract from the goals of global emissions reduction."

Similarly the National Farmers' Federation says it "has no problem with alternative meats", but kangaroo meat has a very limited market.

"Farmers will respond to marketplace demand, but the market (consumers) is not indicating that it will accept kangaroo meat in large quantities – let alone as a substitute for beef or lamb," the NFF said.

"Australian beef and lamb producers are meeting not only domestic, but global, demand.

"An ETS must be designed so that livestock production is not put out of business."