Many took to social media to blast the 33-year-old, but star of the show Kym Marsh has defended Sarah.
Writing in her column for OK! Magazine, Kym, 38, said: "Sarah Harding had a right slating for her performance as Joni Preston.
"I feel for her as it's hard for anyone to come into a long-running TV show with such well-loved characters.
"Sarah's first scene was with Rita in The Kabin and of course she's going to be compared with actors like that."
Like former Girls Aloud singer Sarah, Kym swapped pop star life for the soap in 2006 – after shooting to fame as a member of band Hear'Say.
Kym insists the viewers should've accounted for Sarah's nerves. She continued: "I know I was [nervous] when I came into the show.
"She's come in as a guest artist and I think the way people have been so vocal is a bit harsh."
And mum-of-three Kym praised Sarah for handling the criticism so well. She added: "She's taken it on the chin and got on with it, which is what you have to do."