Marsh won a place on the band when it was formed on ITV reality series Popstars. However, the 35-year-old left the group in February 2002 after a series of rows with the other four members. Writing in her new autobiography, Marsh explained her relationship with Myleene Klass.
"Me and Myleene had a slanging match but someone split us up as we were due to go on air," she wrote of one incident prior to a TV appearnace. "Going on to perform our single was horrible. At one point, me and Myleene had to put our arms around one another. It was so fake and I hated every minute of it.
"We had been overheard arguing by staff at the studios and the following day our row was all over the newspapers. We managed to put it behind us but the niggles remained. I wish we'd been able to explain honestly how we were feeling. But the problems festered."
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Of her eventual exit, Marsh stated: "At the start of 2002, we were invited to play to British troops in Oman but I needed to be in the country for my children. There was a misunderstanding that I didn't want to go to Oman and a newspaper got wind of the story.
"When I asked my PR agent he said that someone in the band had spoken to the newspaper. I felt utterly betrayed. Then I was asked by a newspaper if I had any comment and I was so angry I said, 'I quit'.
The Coronation Street actress continued: "I'm sorry I quit through a newspaper rather than sitting down with the rest of the band. If we could have had a chat to clear the air it wouldn't have been so bitter afterwards."
However, Marsh admitted that she and Klass had had little contact until the death of her son Archie in 2009.
"We hadn't really kept in contact but, being a mum herself, Myleene rang to see how I was," she wrote. "We were both in tears on the phone and, in the days after Archie's death, we talked more and more. Myleene really was there for me. She helped me choose the music for Archie's funeral and sent the most beautiful bouquet of flowers to the crematorium.
"We have both grown up now that we have children of our own. Life is too short to hold grudges and what happened back then isn't anyone's fault. I am determined not to let anything or anyone come between us again."
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