The 'X Factor' judge helped create the girl group when he was a judge on 2002 TV talent show 'Popstars: The Rivals' along with Spice Girl Geri Horner and producer Pete Waterman and is sure the five-piece can get back together if the members, Sarah Harding, Cheryl Tweedy, Nadine Coyle, Nicola Roberts and Kimberley Walsh can get on the same page.
Speaking to The Sun newspaper, he said: ''It needs to be the five of them. They'd do really, really well. If Bananarama could do it, why can't Girls Aloud do it?''
The band played their final concert back in March 2013 after celebrating their 10th anniversary with a greatest hits tour and compilation album bringing an end to their stellar pop career.
Since then the members have all gone in separate directions with Cheryl enjoying solo success on a par with Girls Aloud's chart performance.
Louis, 65, knows a reformed Girls Aloud would do well because they had so many hits, such as 'Biology', 'The Promise' and 'I'll Stand By You'.
He added: ''There would be a huge market for a Girls Aloud reunion.
''They need to delay it for a while but they had great songs, brilliant, brilliant songs - some of the best songs for a long time. And they all look good.''
However, Louis - who has helped guide the careers of the likes of Westlife and Boyzone over the years - ruled out ever working with the girls again.
He explained: ''No, no, no - that would be too tough. It's different with Westlife, as we understand each other and I've never had a row with any of them. Girls are too much trouble.''
Since the band's split Kimberley, Cheryl and Nicola have remained close - the latter even working together in the studio recently - while there's a divide with Nadine and Sarah.
Nadine recently admitted she didn't know the celebrations in 2013 would be so short lived, as she expected new music and further live shows.
She previously said: ''I thought we were going to continue. I thought we were going to do loads and loads of stuff. We had songs, we had a three-album deal and it seemed like a great time. Obviously the girls had different plans.''
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