The proposed introduction of fuel-efficiency-oriented car tax is "not quite rational," Trade chief Kaoru Yosano said Friday.

Yosano made the remark in response to a recommendation issued Tuesday by the Council for Transport Policy proposing the adoption of a tiered auto tax based on fuel-efficiency toward the control of carbon dioxide emissions.

The council, an advisory panel to the Transport Ministry, claims the proposed "green tax" system should also result in neutralizing existing tax revenues by imposing lower taxes on fuel-efficient vehicles and higher taxes on inefficient ones. Yosano told a regular news conference Friday that such thinking cannot be shared by the Ministry of International Trade and Industry.

Yosano speculated that the Transport Ministry is merely seeking a new source of revenue and said the proposal lacks rationality and may further burden car owners already saddled with heavy auto taxes.