Consumer NZ has started a petition calling on the Government to put ordinary people first - saying supermarkets' excess profits are a "slap in the face" to Kiwis struggling to put food on the table.

The watchdog has launched the petition - Stop the Super Profits - and asking the public to get behind it to show the Government and Minister of Commerce and Consumer Affairs David Clark that people want action.

Consumer NZ chief Jon Duffy said they wanted to create conditions for more competition in the grocery sector, which will ultimately result in fairer prices at the checkout.

"We recognise that food prices are going up for a variety of reasons - from the pandemic, to inflation, to the impact of the war in Ukraine on wheat prices.

"We're not disputing this, but excess profits on top of already high food prices are a slap in the face for households struggling to put food on the table."

By 7am, just over 11,400 people had signed the petition.

Duffy said supermarkets were taking more than $1 million in excess profits from shoppers every day.

"These profits are twice what they should be."

Duffy said more competition was needed to drive down prices and give Kiwis a fairer price. But at the moment, that is difficult to do.

"No one is going to start up a competing supermarket without reliable access to wholesale groceries. But the duopoly dominates access to wholesale supply."

He acknowledged the Commerce Commission's recommendation that supermarkets consider supplying other retailers.

"We think this is unrealistic to expect from an entrenched duopoly used to calling the shots. That is why we're launching a petition."

To create what he described as "an even playing field" for new and existing grocery retailers, Duffy said they were calling on Clark to consider regulating access to wholesale supply or setting up a state-owned wholesaler.

Consumer's Sentiment Tracker found people are increasingly worried about the cost of living in New Zealand.

Up to 63 per cent of people in last year's survey picked food and grocery costs as their biggest cost of living concern.

In a recent poll, 98 per cent of those surveyed said they were worried about the price of groceries.