Anyone who has, of late, been pleasantly surprised to find themselves squeezing into a smaller dress size, may be disappointed. A new survey has discovered that deception is afoot with unwitting shoppers being deliberately deceived by a ‘vanity sizing’ ploy used by stores to flatter customers, in which clothes are deliberately made bigger to convince consumers they are buying smaller sizes.

A number of leading high street retail stores, including prominent labels Gap and Marks & Spencer, appear to have employed the deception as their measurements have become larger while the label size remains the same. The study also found a wide variance of sizes across stores dependent on the type of customer the target market is. For example, a Size 10 at Topshop – which is popular among younger women – is likely to be significantly smaller than the more mature aged Zara range.

Marks & Spencer claims that the patterns given to suppliers, or block sizes, have remained the same since 2003, but acknowledged that it had “tweaked” sizes on its website, with measurements increasing by two inches on occasion – equivalent to an extra size.

The study found that a test model, nominally a Size 14 under the British standard sizing chart, became a Size 12 at most high street stores and even a Size 10 at Marks & Spencer. The test further revealed that a Marks & Spencer Size 16 has grown from 38in around the bust, 31.5in around the waist and 41in around the hips back in 2003 to become 39.5-33-43 in 2010.