A mom has branded PrettyLittleThing "disgusting" after she ordered a size 8 dress which was so small it fit her four-year-old daughter instead.

Kirsty Dee took to Twitter to vent her fury at the brand, sharing a photo of her little girl, Molly, wearing the black dress.

She hit out at the clothing company saying she was "so angry," as she had bought the dress for a birthday party, but now couldn't wear it.

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Kirsty had bought the classic LBD, which featured a t-shirt cut, but when she tried on the dress she could barely get it over her head.

The mom later tweeted out a photo of the dress — clearly showing the size eight label — alongside Molly modeling the frock.

"I just think it's disgusting how they promote body confidence and then send me a dress not fit for a size 6 - 8," Kristy told Fabulous Digital.

"Made me feel awful at first but laughed it off when I saw it fit my 4-year-old. I couldn't get it over my head," she added.

"I was so angry, I bought it for my friend's birthday BBQ the day after."

Kirsty bought basic black pocket detail T-shirt dress, for 10 pounds, or about $12.70, and it also comes in sizes six and four.

(PrettyLittleThing)

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She vented her fury at PrettyLittleThing on social media, tweeting: “So bought this in a size 8 from @OfficialPLT wouldn’t even go over my head and just fits my 4 year old daughter! Really?????”

After Kirsty called out the retailer on social media, they responded to her and apologized for their mistake.

“So sorry to see that there is an issue with the dress you bought," the company wrote. “If you could please drop us a DM with your order number and the name of the item we can look into getting this sorted for you.”

Fabulous Digital has reached out to PrettyLittleThing for a comment.

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The brand also came under fire from another shopper, who claimed to have bought a playsuit covered in blood.

PLT, however, is also selling giant festival wings, and fans are apparently loving them.

This article originally appeared on The Sun. Read more content from The Sun here.