Choice says an increasing number of females say they're forced to shop online or at chain stores because they can't fit the stylish clothes sold in shopping malls or high street stores.
Retailers who say they are struggling should consider expanding their range to fit the growing number of women who wear size 16 and above, Choice spokeswoman Ingrid Just says.
"What we're essentially identifying is that there is a whole market out there that many designers and retailers aren't necessarily tapping into."
"Consumers are finding themselves quite frustrated by not being able to buy clothes that suit their bodies."
Part of the issue was the fact that there was no standardised clothing sizes in Australia, Ms Just said.
"The other part is the fact that they're simply not making clothes that fit the average Australian body like they used to, except for a couple, a handful, of labels."
Ms Just says larger women are having to shop at chain stores such as K-Mart and Target to find clothes that fit their bodies.
Shopping malls and high streets stores cater for size 10s and 12s, but 14s vanish quickly from the shelves and it is very difficult to find a size 16, she said.
Larger women who want to wear stylish clothes say they are forced to shop online at US and UK stores which do better in this area compared with Australian retailers, Ms Just added.
Larger women are also paying more than slim women.
"Some of the shoppers that we've spoken to said that in some instances they're paying double what a smaller woman might pay," Ms Just said.
Choice suspects some designers and retailers shun plus sizes because they want their label and fashion to target a particular demographic, or particular "look" or body shape.
"It's certainly within a designer or label's right to market and to design for a particular type of customers that they want to wear their clothes," Ms Just said.
"But at the same time, if they're concerned about falling retail sales and the difficulties of getting more customers in store versus shopping online, then this is an opportunity for them that they shouldn't overlook."
Do you think larger women lack clothing choice and are paying too much?