Research found half of women aged 16 to 44 struggle to buy garments that are their size because of confusion over standard measurements which sees them slip into a size 12 dress in one store and burst out of it in another.
As a result, three in four female shoppers said they would like to see size standardisation across retailers.
Every fashion brand has its own system, meaning there are often enormous differences in the measurements for the hips, waist and bust.
Meanwhile, a number of stores have inflated measurements for standard sizes to reflect the fact that women are getting heavier, with thicker waists and hips and bigger breasts.
However, a survey by market research firm Mintel suggests women are becoming increasingly frustrated that high street stores do not abide by the same templates.
Women are finding it so difficult to buy well-fitting clothes that more than one in three frequently pay for alterations, Mintel said.
They also found many women feel let down by store assistants, who are unwilling or unable to give advice.
Almost two in five said they are not confident about which clothes best suit their shape or size and they would welcome some guidance when trying things on.
And more than half said that they would be willing to pay more for items that fit them perfectly.
Tamara Sender, senior fashion analyst at Mintel, said: “The fact that consumers are willing to spend more on clothes that flatter them highlights just how important it is for retailers to focus on designing clothes that are cut to fit well and use the correct fabric to improve the way a garment falls.
“Currently, there are huge variances between retailers, with a size 12 for example fitting differently depending on the retailer or brand, meaning customers cannot automatically know whether a garment will fit them.
“There is a real need for retailers to more accurately manufacture clothes so there is consistency in sizing.
“Retailers can also do more to help shoppers find the correct fitting clothes and there is scope to have staff with additional training in tailoring skills on hand in changing rooms who know how to measure a customer and advise them on what fits.”
The confusion seems to result from the fact that fashion brands have failed to keep up with changes in body shape over the last 50 years.