The Tribunal had in July last year ordered de-registration of diesel vehicles older than 10 years and scrapping of diesel vehicles older than 15 years.

Appearing before a bench of Justices Madan B Lokur and P C Pant, Attorney General MukulRohatgi and additional solicitor general Pinky Anand said the NGT directions were arbitrary and against the Constitutional provisions and there was no scientific or rational basis for banning diesel vehicles. The government even contended that diesel was a better and less polluting fuel than petrol in some respects.

"Scientific literature does not show that diesel is worse off fuel than other fuels on which automobiles run in the NCR region. Petrol vehicles cause higher carbon dioxide pollution, CNG vehicles causes higher nitrogen dioxide pollution and diesel vehicles have higher PM pollution," the Centre said in its appeal.

"Diesel vehicles, however, have higher fuel efficiency in comparison to petrol vehicles. Diesel vehicles emit 10-15% less carbon dioxide as compared to petrol vehicles. Diesel vehicles also have higher fuel efficiency. There exist exhaustive scientific evidence to show all vehicles of petrol, diesel and CNG cause some pollution or the other," the petition said.

The government said pollution caused by diesel vehicles represent a minuscule proportion of pollution. Diesel vehicles save over 1.5 million tons of carbon dioxide emissions in a year. "It is submitted that even European countries and Japan are promoting diesel vehicles. By cutting short the economic utility to be derived from a vehicle which is otherwise useful and is legally permitted, national loss as well as personal loss of livelihood and freedom of choice is being caused to the owner of the vehicle," it said.