Therese Alshammar of Sweden has been stripped of a world record after it was found she wore two swimsuits during a race at the Australian national championships.
Swimming Australia banned the use of multiple swimsuits after last year's Beijing Olympics because of concerns about extra buoyancy.
The sport's world governing, FINA, introduced a similar rule last week.
The 31-year-old immediately lodged an appeal.
Alshammar broke her own 50 metres butterfly world record yesterday during heats at Sydney's Olympic pool.
She recorded 25.44 seconds, taking 0.02 seconds off the record she set Barcelona in June 2007.