"I know some people wash new clothes before they wear them, but you shouldn't HAVE to wash them first, unlike this supposedly "brand new" jumpsuit I bought on
@ASOS," she wrote, adding: "Yes, this is SOMEONE ELSE'S PERIOD BLOOD. And it's handwash only."
It left social media users equally as disgusted with Ms Williams' horrifying find on the £40 ($NZ80) sale item.
A furious woman posted this image on Twitter after buying a jumpsuit from ASOS with a period stain in the crotch. Photo / Twitter
The shopper said she had put on the flower-patterned jumpsuit on Tuesday with the intention of wearing it to work that day.
"It's backless, so I took it off to put another layer on underneath. It was only when it laid inside out that I saw the bloodstains," she told The Sun.
"For a second I thought I must've started my period early (I hadn't) but on closer inspection it was very obviously someone else's dried period blood."
She said that after realising it wasn't her period – the discovery made her feel "physically sick".
"So, so gutted. Really shouldn't have to check for stains on a brand new item," she later wrote on Twitter.
After tagging ASOS in her original tweet, the brand responded several times asking her to direct message with all the details "and we'll be happy to help".
Well, @ASOS say they have processed a refund but I need to call Trading Standards back if it’s not in my account within 14 days. So, so gutted - can’t believe I almost wore it! Really shouldn’t have to check for stains on a brand new item 🤢🤮
However, according to the shopper, they were a "string of automated direct messages with conflicting information", making contacting the company difficult.
She later told The Sun that in a private Twitter conversation, ASOS reassured her it would refund the money.