China's parliament has proposed increasing tax benefits for companies that cut pollution by more than the national standard, state media reported on Monday, the first details of a much-anticipated new code aimed at curbing the country's emissions.

If the plan is passed by the National People's Congress, China's top legislator, companies that reduce emissions to half of the national requirement would only pay half the taxes levied for air, water and soil pollution, Xinhua said.

Companies in the agricultural and transport sectors would be excluded from the new tax law, state radio said. Those industries are much smaller polluters than sectors like steel, coal and oil.

The government won't tax companies for their carbon emissions as that is essentially already done by China's carbon market, which gives companies an incentive to limit their emissions by issuing emissions permits.

No other details on the proposal were disclosed.

The government has been discussing the new tax law for years, which is aimed at cutting pollution, particularly from heavy industry.

(Reporting by Beijing newsroom, Josephine Mason and Kathy Chen; Editing by Susan Fenton)