"Are your vehicles emitting oxygen?" was the Supreme Court's withering reply to car manufacturers including Toyota and Mercedes, who want a ban on their larger diesel cars in Delhi to be revoked.
Automakers like Mahindra & Mahindra Ltd have asked the court to reconsider its temporary ban, introduced last month as part of an effort to check Delhi's toxic smog.
The top court had ruled that cars with engines of more than 2,000 cc in capacity cannot be sold in the capital until March 31. A World Health Organization study showed 13 of the world's 20 most polluted cities are in India, and Delhi tops the list.
Manufacturers like Mercedes countered in court that their larger cars and SUVs are not as damaging for the environment as believed, that internationally, diesel cars are becoming the norm, and that large cars like Boleros and Sumos are used by the common man and in rural areas.
The judges today disagreed, but asked the manufacturers to furnish documentary evidence to prove their claim. "Which class of people are using 2000cc vehicles? It's used by the rich only. You are saying diesel vehicles pollute less. So are your vehicles emitting oxygen?" the judges asked.
The court said it is considering expanding the ban to diesel cars with engine capacity of less than 2,000 cc - currently not covered - but will first seek industry input on the matter.
It was also expected to rule on a separate green tax on all diesel cars in the city, but has yet to announce its decision on that levy.
The temporary ban on large diesel cars ordered by the Supreme Court on Wednesday has unsettled India's car industry. It says an uneven, haphazard policy makes it hard to plan investment and allows damaging regulatory arbitrage across states.
The government was pulled up today with the judges asking why it's using diesel vehicles that are older than five years. "How can the government be a polluter?" the judges asked.
The Supreme Court has also restricted the entry points into Delhi for large commercial vehicles and trucks that are headed to other states.