Three little letters. That’s all it took to spark a nasty verbal cage match between outgoing Woolworths chief executive Brad Banducci and the chairman of the Senate select committee into supermarket prices, Greens senator Nick McKim.

After a predictable prepared statement about the level of competition in the supermarket business from Banducci – repeating the justifiably well-worn point that the net profit margins of Woolworths and rival Coles are actually around 3 per cent – McKim took aim with a deceptively simple question.