Westlife decided to split because they have "lost ambition".
The Irish quartet will go their separate ways at the end of a farewell tour next summer and although their manager Louis Walsh was unhappy with the decision, the group felt it was the right time to call it quits as they are no longer as focussed on the group as they once were.
Nicky Byrne said: "As a band, though not individually, I think we have lost ambition. As soon as your hunger goes, you have to face facts, man-up and make the decision."
While Kian Egan calls former member Brian McFadden a "loony tune" for quitting the group in 2004, they haven't ruled out a reunion with him on their farewell tour.
Kian said: "I am not going to lie. I love Brian as a person. He is a fantastic character, he'd give you the shirt off his back. But he is also a loony tune.
"I thought once one member of the band leaves at that early stage, that's it. I was probably the one to have that reaction more than anybody else. I thought we were done and dusted, and I found it strange at the time why he would want to do that.
"He couldn't cope with having four other guys telling him he had to do things. He wanted to be his own person and be the free spirit that he actually is."
Nicky added to the Daily Mail newspaper: "But we have been out with him since and discussed our careers. If he was to ever do anything again with Westlife, that would be very special.
"For different reasons it may never happen - ever. Or it might happen on the last tour. I think it would be nice, and I hope we do sing with him again one day."