Food manufacturing company Griffin's wasn't aware of a potentially life-threatening peanut contamination in its chocolate raisins until a customer called in to complain.

The admission has shocked a leading allergy specialist, who is now calling for an overhaul of the way the company handles its food production.

Griffin's confirmed a packaging error saw its chocolate raisin packets filled with chocolate-coated peanuts. They have recalled a specific batch -- 100g packs of 'Eta' chocolate raisins carrying a best before date of May 2, 2017.

People who suffer from peanut allergies can have serious life-threatening reactions, including anaphylaxis, swelling of the throat, low blood pressure, breathing problems and hives.

Griffin's spokesperson Barry Akers said the chocolate raisin packaging was accidentally left in the packing machine when production was switched to chocolate peanuts.

Staff then failed to notice the mistake, as the packets were "very similar" and weren't able to notify the authorities until a member of the public called in to complain.

Dr Vincent Crump of Auckland Allergy Clinic said the mistake could have killed someone and the failure to notice the mix-up was "not acceptable".

"They should have cross-references and cross-checks to prevent this from happening," he says.

"It's absolutely shocking. The public shouldn't be the one who have to find out the hard way for something like that."

He also criticised the physical set-up of the production line, saying Griffin's should package the common potentially deadly allergens on a completely different line to other non-allergenic foods.

"Human errors will happen, but if you have the physical structure or platform to prevent these accidents then it's impossible," he says.

"I would say they obviously didn't take enough care, because if they did they would have figured it out before the product got out into the marketplace. I hope this would be a lesson, because somebody could have died from it."

Mr Akers said he was "unable to respond" to some of the critique, in particular claims that the company should have noticed the botch-up before it went to market. However, he pointed out that Griffin's had immediately issued a recall when it became aware of the issue.

"It's fair to say a mistake was made, and mistakes are actually quite rare. But they're made in every industry, and it's about how you respond to the mistake. There is an element of human error in every production process," he says.

"They've certainly had an internal inquiry and they understand now how the mistake was made."

The product is widely sold in retail outlets and major supermarket chains throughout the country but has not been exported internationally.

Those affected can return the product to their retailer for a full refund.

Newshub.