The star also spoke up for actress Michelle Collins, who has come under fire for her portrayal as Stella Price on the soap, saying that it is "unfair to blame" her.
"Not only is it unfair to blame Michelle Collins for a fall in Corrie's viewing figures, it's also incorrect," she wrote in her New! magazine column.
"As our producer Phil Collinson explained last week, a newspaper used an episode that was up against a Wimbledon match to illustrate a drop in figures. Big sporting events always affect viewing figures."
Marsh also criticised former Coronation Street actor Johnny Briggs, who recently said that he found the soap had lost its fun and humour.
"I thought that former cast-member Johnny Briggs's comments that there is no humour in Corrie were harsh, too - particularly as he admits he doesn't watch the show!"
William Roache also recently defended producer Phil Collinson over the show's performance.
Executive producer Kieran Roberts described reports that the loss of viewers related to the soap's increase of gay characters as "a storm in a teacup".
Kym Marsh had recently asked for Coronation Street fans to give Michelle Collins a chance to settle into her new role.
Read the full story in this week's New! magazine - out today.