Jesy Nelson has pulled out of her presenting role in Saturday evening's live final of Little Mix: The Search.
The 29-year-old was due to appear alongside her bandmates in the last episode of the BBC One talent show.
But a spokesman for the group said in a statement: "Jesy is unwell and will not be appearing on tonight's final of Little Mix The Search.
"She will also not be hosting or performing at tomorrow's MTV EMAs [Europe Music Awards]."
The statement, which was made on Saturday morning, did not make clear what is wrong with Nelson or how unwell she is.
The announcement comes the day after Little Mix released their sixth album, Confetti.
The group were due to host the MTV EMAs on Sunday evening, which will be filmed in various locations around the world due to the Covid-19 pandemic.
It is thought Leigh-Anne Pinnock, Perrie Edwards and Jade Thirlwall will still host the ceremony, which will feature performances from Doja Cat, Sam Smith, DaBaby and Alicia Keys.
media captionLittle Mix say the pressures associated with an online presence can be harmful to young people's mental healthLast month, filming on Little Mix: The Search was halted after a "small number of people" involved in the series tested positive for Covid-19.
The band were not among those who tested positive, but Thirlwall self-isolated as a precaution.
She still took part in the first live show virtually, dialling in via video link to judge and score the bands from home.
Around two million viewers have been tuning in to each episode of Little Mix The Search, which has been airing since late September.
The task for the group is to assemble six bands from thousands of wannabes, and eventually choose one to support them on tour.
Nelson has previously discussed her mental health battle on the BBC Three documentary Jesy Nelson: Odd One Out.
The documentary, which won a National Television Award, addressed body image and the impact of online bullying.
In the programme, Nelson revealed that negative comments online had led to an attempt to take her own life.
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