The one-off job will see Harding appear on the final of the the talent contest alongside host Stephen Mulhern on a celebrity panel.
A show source told the paper: “Sarah is delighted... She’s been offered the gig on the night of the final which, obviously, will be the biggest TV audience of the series so far.”
She told the Daily Star: "I'd consider [The X Factor], definitely. I would love to be a mentor.
"If I feel someone has talent and potential I can always see it in them. I'd love to do that."
Meanwhile, Harding was banned from driving for six months and fined £500 earlier this month after pleading guilty to driving while talking on her mobile phone. She already had nine points on her licence from three previous speeding tickets dating back to 2010.