According to an article in The Guardian (1), the "World's top firms cause $2.2tn of environmental damage, report estimates". That's 2.2 trillion dollars per year that governments are effectively subsidizing to help out the top 3,000 biggest public companies. The report also notes that if those companies were forced to pay for the costs they're passing onto others it would eliminate about 1/3 of their profits.
The debate over to what extent the government should interfere with the free market is important and legitimate. However, knowing that governments are subsidizing a third of the yearly profit of the world's top 3,000 biggest public companies - so they can pollute cheaper - it's difficult to come to the conclusion that the free market calls for increased subsidies to big businesses.