Taking to the stage in monochrome ensembles, the four-piece girl group belted out their hit single Wings in honour of the 22 people killed in the terror attack last month.
But, despite their show-stopping performance, it was their choice of attire that got many people talking on social media.
The X Factor winners flashed plenty of flesh on the night as Leigh-Anne Pinnock wore a bra and eye-caching trousers while Jesy Nelson opted for a high-cut bodysuit that revealed plenty of leg and showed off her peachy posterior.
Little Mix were criticised for their choice of outfit
Little Mix took to the stage in monochrome ensembles to perform Wings
Jade Thirwall also showcased her derrière in a pair of thong-style high-wasited shorts, whereas Perrie Edwards was slightly more covered up but still teased her cleavage in a busty bralette.
Flocking to Twitter, viewers slammed the band for their "embarrassing" stage costumes.
One person wrote: "In tears… I’m not normally a softie… well done ariana xxxx respect shame little mix were half naked #OneLoveManchester."
"I know it's little mix's thing to dress inappropriately but you'd think they'd put clothes on for such an important event, no? #OneLove," said another viewer.
The girl-group performed at One Love Manchester Little Mix in pictures Mon, June 5, 2017
Little Mix stars Jesy Nelson, Perrie Edwards, Leigh-Anne Pinnock and Jade Thirlwall in their sexiest pictures.
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Little Mix perform on stage during the One Love Manchester Benefit Concert
The X Factor winners belted out their top single on the night
"OMG how embarrassing – Little Mix forgot their clothes #OneLoveManchester," stated one person, while another added: “Little Mix in revealing outfit shocker! #OneLoveManchester."
However, many fans hit back at the critics online as one viewer wrote: "How dare people judge their clothes instead of applauding them for been a part of this #OneLoveForManchester #LittleMix."
Another added: "Stop moaning about the outfit choices of @LittleMix and just watch the show. Remember why the girls are doing this #OneLoveManchester."
Viewers complained about Little Mix's choice of outfits
Jesy Nelson and Jade Thirwall flashed their pins and posteriors
Ariana Grande put on the benefit concert for the victims of the Manchester bombing
Little Mix were joined by a host of international stars on the night to raise money for the victims of the Manchester bombing at the end of Ariana Grande’s gig on May 22.
The 23-year-old popstar also dedicated one of her performances to victim Olivia Campbell, after her mother Charlotte said she would have wanted to hear one of her hit singles.
One Love Manchester concert is now available on BBC iPlayer.