A TV ad showing a girl going online to ask where to insert a tampon has sparked outrage.
Advertising standards watchdogs in New Zealand and Australia have received complaints about the Carefree tampons commercial, along with a second one.
The ads have been described by viewers on the firm's Facebook page as "unnecessary filth", "disgusting" and "tasteless".
One shows a schoolgirl asking Google if she is putting her tampon in the right place. The other features an amorous couple in the back of a car with a stream-of-conscious voice-over saying: "And then I remembered I was wearing a pad."
Carefree is standing behind the "honest" advertising campaign, saying many girls are anatomically confused and do not know where tampons should go.
One disgruntled viewer wrote on the company's Facebook page: "How low and degrading towards women everywhere"
TVNZ said the ad featuring the schoolgirl was screening only on TV2, and only after 7pm.
A Carefree spokeswoman said the realities of tampon use might be uncomfortable but were a normal part of life for women.
Research commissioned by the company showed women of all ages were misinformed and too embarrassed to ask questions about menstruation.
The research also found an abundance of young girls unsure how to use a tampon properly.
The campaign was to reassure women, particularly young girls, that periods were natural and all women go through a learning curve. "Our aim has been to tackle menstrual health taboos and address girls' concerns with honesty."