X Factor bosses have reportedly sparked fury among medics after claims that finalist Marcus Collins was allowed to have Botox jabs backstage.

According to the Mirror the singer has undergone four treatments before performances on the show – and last week was allegedly forced to wear a hairpiece after one of the injections went wrong.

He has since been seen wearing a woolly hat amid claims that the treatment made him appear to have a receding hairline.

“Marcus has admitted using Botox but it’s not an official treatment set up by bosses,” an insider told the paper. “He denies using a hairpiece on the show.”

However experts have spoken out against the injections, with Vivienne Paterson of Mediawatch calling it “a bad example for younger viewers”.

And Harley Street Skin Clinic specialist Lesley Reynolds Khan told the paper, “The people looking after him should be saying no. He has a whole lifetime to worry about lines.”

A spokesman for the show said they were “not aware” of any contestants having Botox backstage – but added that there was a beautician on site every week to offer treatments.