Girls Aloud "didn't like each other".
Louis Walsh, the girl band's original manager, insisted that the quintet - Cheryl Fernandez Versini, Nicola Roberts, Kimberley Walsh, Nadine Coyle and Sarah Harding - did not get on and claimed that Nadine was the only member who could sing.
Speaking on Kate Thornton's 'Paper Cuts' on BBC Radio 2, Louis said: "I didn't give them a lot of my time but they didn't give me time and they didn't even like each other!
"It was problems from day one there. I contacted them as much as I could but they didn't like each other.
"It was never going to work because I said Nadine was the best singer and she was. She was the voice of Girls Aloud."
Louis went on to say that Nadine would have been a bigger solo star if she had married a soccer player like Chery - whose first husband was Ashley Cole.
He said: "Nadine was the only real singer there.
"She should have married the footballer. Look at Victoria Beckham, it worked for her. And Louise [Redknapp]... and wasn't Cheryl married to a footballer?"
Louis, 63, and Cheryl, 32, have feuded since he managed Girls Aloud from 2002-2005, and the Irish music mogul - who previously branded Cheryl "lazy" and "irrelevant" - previously advised her to get away from the spotlight and work on another successful song.
He said: "She's lost a bit of energy. She should go away, make a record and maybe have another hit."