In a warning to Indian carmakers, Union Transport Minister Nitin Gadkari today said that the government will have no option but to increase tax on diesel vehicles and make their sales “difficult” if manufacturers do not limit their production. “Say goodbye to diesel… Please stop making them, otherwise we will just increase the tax so much that it would become difficult to sell diesel cars,” Mr Gadkari said while speaking at 63rd Annual SIAM convention in New Delhi