A corresponding sign for the Pak'nSave trolley of goods was placed on the top of the trolley under the clear wrap.
A sign stood in front of the trolleys reading; "These trolleys of grocery items were purchased at Countdown Rotorua and Pak N Save Rotorua on the same day (16.06.11)".
In the complaint, Foodstuffs stated the comparison wasn't fair as the items in the trolleys were not comparative.
In its decision the Advertising Standards Authority (ASA) stated the promotion breached standards in failing to compare like products and using far more items on special to make the Countdown trolley look cheaper than it was.
The authority's chief executive, Hilary Souter, said complaints of this nature were a long-standing issue and needed to be resolved.
She said price was paramount to consumers and advertisements comparing products needed to be fair representations.
"The reality is that this kind of process is being used a lot," she said.
"We have now set a precedent and people know that this sort of advertising is not acceptable."
Rotorua Pak'nSave owner Neil Foster couldn't not comment on the decision but Foodstuffs legal general manager Mike Brooker said the company was "very pleased" with the ruling.
"It vindicates out view that their advertisement was misleading. It was not a direct price for price comparison," he said.
A spokesman for Progressive Enterprises could not be contacted for comment.
Rotorua budget advisor Pearl Pavitt said consumers needed to be aware such advertising was happening.
"To have a fair comparison you really need someone independent to go in and buy the same products from each store."
She said consumers needed to be sure about what they wanted to buy before they went shopping.
"People will drive from one place to another trying to find the best bargains and save some money. What they are actually doing is wasting more time and money because they are wasting petrol."
She said people should look at what was on offer in each store, then pick which supermarket had more of what they wanted and shop there.
"Only shopping by the specials can be a waste of time."