Bra fitting services at high street stores fail to measure up to expectations, according to a survey.
Less than a third (29%) of bras sold in an undercover investigation were rated as a fit by experts.
Consumer champion Which? sent 11 mystery shoppers to buy underwear with the help of staff during 70 visits.
The volunteers, aged 25 to 75, were DD cup-size or bigger.
Around a quarter (18) of the 70 fittings were given scores of zero for the study and no store's service was deemed good enough to recommend.
Experts suggested the customers who experienced the worst fittings would have been better off "picking something off a market stall".
Some of the women were sold different sizes by different shops, the survey found.
In one case this varied by seven sizes from a 34FF to 40D, while another woman was sold the same bra in two House of Fraser branches but in sizes 34C and 34F - neither of which were a good fit, Which? said.
Badly fitted bras can cause neck, shoulder and back ache and poor posture, as well as affecting appearance.
Consultant bra technologist Gillian Spencer and lecturer and technical designer Laura Savery assessed the fit of bras sold to the researchers. They looked at the fit and comfort of cups, wire and straps.