New Zealanders are boiling mad over a recipe tweak to their favourite chocolate milk drink Milo, labelling the new taste "crapola" and "disgusting".

Milo has been a Kiwi favourite for more than 80 years -- mixed with either hot or cold milk, and sometimes, when parents aren't looking, scooped up in spoonfuls straight from the tin.

But food giant Nestle recently altered the recipe to reflect "children's nutritional needs" and the change has outraged normally laid-back New Zealanders.

"The new Milo tastes disgusting why would you change the recipe!" Daniel Glubb said on a Facebook page calling for a Milo boycott that has attracted more than 6,000 likes.

Josh Rogan commented: "OMG! Just tasted the new Milo. I can't believe the taste difference. It is not nice & is not a 'slight change', I am gutted this has happened."

Nestle insists the essential ingredients remain the same -- malted barley, milk powder, sugar and cocoa -- but the new version has added vitamin D and switched to sustainable palm oil, while vanilla flavouring has been removed.

But Lizzie Buckthought objected to the inclusion of any palm oil at all, saying it had no nutritional value and affected the taste of products it was used in.

"Why palm oil??? It's made other products taste like crapola. What made you think it wouldn't do the same to yours?," she wrote on Facebook.

Nestle spokeswoman Margaret Stuart said the company had been surprised by the extent of the reaction but had no plans to revert to the old recipe.

"To have such a backlash over what is a small flavour shift is surprising," she told TV3, adding that the new recipe reflected research on children's nutritional needs.