Paulin alleged the supermarket chain had breached those rules through online advertising relating to the advertisement of DB Export Beer which was advertised with a discount of 26.1%.
Paulin said the situation was not isolated to one store.
Ashburton New World owner Jeremy Rooney was cross-examined on Monday morning.
He was asked by the prosecution why he did not know that the advertisement was not legal.
“There are 18,000 products in my store, to know the price of all of them is not possible.”
Rooney told the court the supermarkets received the planned sales about four weeks ahead of them going live, but it did not show the discount percentage, only the cost price, sale price and GST.
The hearing continues.