The Chinese government has unveiled a detailed roadmap for a national emission trading scheme in a significant sign the world's largest greenhouse gas emitter will introduce a country-wide carbon price. Speaking in Washington, the deputy director of China's powerful National Development and Reform Commission, Wang Shu, backed a national scheme, saying it could provide ''an efficient and lower-cost approach for addressing climate change and realising low carbon development''. The speech to an arm of the World Bank last week preceded the political debate around carbon pricing in Australia flaring again on Monday, with the Coalition renewing its vow to scrap Australia's carbon price and replace it with a ''direct action'' policy. Australia introduced a national carbon price in July last year at a fixed price - often called a tax - of $23 per tonne of carbon dioxide emitted. It is designed to become a fully fledged emissions trading scheme in mid-2015. In China, an emissions scheme would be built on regional pilot schemes due to start this year in five cities and two provinces. Mr Wang said China would turn its focus on implementing a national market from 2015. ''It is going to happen that development of ETS [sic]. The only problem is how to improve it step-by-step,'' his presentation says. China's submission to the World Bank's Partnership for Market Readiness program says it anticipates a full national trading scheme will be ready during its 13th five-year plan period between 2016 and 2020. Mr Wang said disagreement still exists over a separate carbon tax for China. He said there was no confirmed schedule and a tax was still being studied and coordinated. China is the world's largest greenhouse gas emitter and burns nearly as much coal as the rest of the world combined. It has a target for reducing carbon dioxide emissions per unit of GDP 40 to 45 per cent below 2005 levels by 2020. Australian National University's Dr Frank Jotzo said the work program signalled China was serious about a national trading scheme. The Chinese submission says research will determine which industries would be covered and that $66 million has already been committed by its government. Mr Wang said China would co-operate with other countries for capital and technology support.