Low income parents can't afford to properly feed their kids.

A study's found the number of kids hospitalised for malnutrition has doubled in the last decade.

Around 120 children have had to stay at hospital overnight because of nutritional deficiencies.

GP Dr Nikki Turner said people on low incomes don't make worse food choices than others.

She told Mike Hosking they're spending more than half their money on food, but can only do so much.

"The lowest incomes in New Zealand are too low to be able to effectively feed our children well. people will stock up on very cheap poorly nutritious food."

LISTEN ABOVE AS DR NIKKI TURNER SPEAKS WITH MIKE HOSKING