Walmart Canada is facing criticism for charging more for plus-size clothing, a policy some shoppers consider an unjust "fat tax."

"It's unacceptable," said Walmart shopper Shannon Mozak, of Edmonton, who sometimes buys plus sizes. "It's a form of shaming people."

Walmart and some other retailers mark up their plus-size clothing with the justification that bigger sizes cost more to produce.

They also charge a single lower price for a wide range of standard sizes — from extra small to extra large — leading many plus-size shoppers to question why only they must pay more.

Michaela duChêne didn't know she was paying more for plus-size clothing at Walmart until she saw this sign at one of its locations in Sydney, N.S. (submitted by Michaela duChêne)

"It's not right," said Michaela duChêne, who wasn't aware she was paying more for Walmart's plus sizes until an in-store sales sign revealed a price difference.

Posted this month at a Sydney, N.S., location where she shops, the sign advertised George brand women's T-shirts for $9.97, but stated 1X to 3X plus sizes cost $2 more — an increase of 20 per cent.

A check of Walmart Canada's website found that women's plus-size clothing items made by George — a brand exclusive to the chain — cost between 10 and 30 per cent more than the exact same items in regular sizes, which include extra-extra-large.

According to Walmart Canada's website, women's regular size yoga pants are 31 per cent cheaper than the same item in plus sizes. (Walmart Canada)

Walmart U.S. also charges more for George brand plus sizes.

But not all retailers follow that policy: Canadian clothing chains Joe Fresh and Reitmans charge the same price for both plus and regular sizes — a policy duChêne applauds.

"There should either be one price for everything, or every single size should be a different price," she said.

Men's large costs less

Mozak, in Edmonton, also takes issue with Walmart's pricing policy. When trying on different sizes of a George jacket last month, she noticed the 1X plus size — priced at $25 — cost $5 more than the regular sizes.

Mozak ended up buying the exact same jacket in a men's large, which felt slightly roomier than the women's 1X plus size, but — to her surprise — it was $5 cheaper.

"The same amount of fabric is being used to make men's clothing and they aren't charging them more for it," she said.

"Why are plus size women paying a tax for their clothing?"

Walmart Canada also charges more for George men's plus-size clothing compared to regular sizes.

The retail giant said it charges extra for plus sizes because they can be more costly to make.

Walmart Canada charges $15 for this woman's hoody in sizes XS to XXL, and raises the price to $17 for plus sizes. (Walmart Canada)

CBC News asked the retailer why it charges the same price for a woman's item in an extra small and an extra-extra-large but raises the price for the 1X plus size — which has similar measurements compared to the regular-sized XXL version.

Walmart replied that it generally prices its clothing based on the average cost of a series of sizes, such as XS to XL.

"A size XS and XL may not have the same production costs but will have the same retail price," Walmart spokesperson Anika Malik said in an email.

The same rule applies to the retailer's 1X to 4X plus sizes, which are grouped separately, she said.

Walmart is now exploring ways to reduce the extra costs involved in making plus-size clothing to lower their retail price, Malik added.

Sending a negative message?

Professor of fashion Ben Barry said when manufacturers produce clothing on a mass scale, the cost difference for larger items is negligible.

"It really doesn't have a significant impact on your bottom line," he said, "because you're ordering material in such large quantities."

He also warns that retailers charging more for plus sizes could wind up paying a high price — if customers take offence.

"You're sending such a negative message to plus-size women that you're going to lose that consumer base," said Barry who chairs Ryerson University's school of fashion in Toronto.

An ad for Joe Fresh clothing promoting the fact it charges the same price for regular and plus sizes. (CBC)

In May, London-based retailer New Look sparked outrage and made headlines in the U.K. after it was revealed the chain charged more for plus-size clothing.

New Look said it has now changed its policy to charge one price for all sizes.

In 2014, Old Navy made news in the U.S. following a petition protesting the retailer's policy of charging extra for women's plus sizes but not for men's plus sizes.

​Old Navy said in an email this week that its women's plus sizes are a "specialty line" which includes special fabric and "curve-flattering elements."

Nevertheless, the retailer said it's narrowing the price gap and eventually plans to charge one price for all sizes.

Michaela duChêne in Syndey, N.S. doesn't think it's fair that she has to pay more for plus size clothing at Walmart. (submitted by Michaela duChêne)

Meanwhile, after her experience, Mozak plans to stop buying plus-size clothing at Walmart.

DuChêne said she'll continue shopping there for clothes, because she has limited options in Sydney.

But she said her Walmart shopping experience has been sullied somewhat, now that she knows she's paying more to buy something in her size.

"It kind of just gives you a sour taste in your mouth."