Coles and Woolies have monstered the Australian grocery sector to the point where they now enjoy the highest market concentration for supermarkets in the developed world.

Their businesses – from pokies to hardware stores – are an inescapable part of modern Australian life.

In fact, on average, every Australian man, woman and child spends $100 a week on products owned either by Coles (or parent company Wesfarmers) or Woolworths.

With such power comes responsibility. But just who do the “big two” owe responsibility to?

Shareholders, first and foremost.

Until recently, Woolies enjoyed double-digit annual growth for a decade and Wesfarmers quadrupled its share price in the same period.

Their responsibility to customers extends as far as creating a perception they are keeping prices low.

At a time when cost of living pressures are front of mind for shoppers, Coles and Woolies are furiously jostling for the position of price leader.

And too often suppliers become collateral damage in that fight.

The supermarket giants’ ferocious buying practices have spawned a thousand stories of suppliers being screwed down beyond breaking point.

Many of those suppliers are in the rural sector, although you rarely hear Nationals MPs take up the cudgel for them.

It’s really only the crossbenchers that speak openly about giving courts the power to break up the duopoly.

No business, and certainly not a voracious corporation, has a responsibility to their competitors.

And so it has proven with Coles and Woolies, which have used their buying power to paralyse a growing number of sectors –  small grocery, liquor, petrol, butcher and hardware stores, just to name a few.

They’ve also launched a price war on household staples, including eggs, bread and milk. In recent weeks, the war has extended to barbecue chooks.

These “loss leaders” put competitors in an impossible position.

And that’s precisely how the supermarket bullies like it.