Westlife decided to split after their plan to leave Simon Cowell's record label failed to repair the "cracks" in the band.
The Flying Without Wings hitmakers have announced they are to hang up their mics in 2012 following a greatest hits tour, after 14 years together.
They have insisted the split will be for good and that the move is not a publicity stunt, revealing they turned down millions to carry on.
Now Nicky Byrne admits the singers knew they had to go their separate ways after leaving Cowell's Syco imprint earlier this year (11), as the move did not improve relations within the band as they had hoped.
He tells Britain's Daily Record, "The cracks had formed and we were trying to patch things up when we left Syco, rather than quitting. We thought we would try and change everything to see if things improved and it wasn't to be.
"It wasn't one thing just a gradual progression. The amount of pressure to constantly do it at the right level was huge.
"There have been cracks internally for quite a while. Because we were releasing a greatest hits this year and re-negotiating our contract, it felt the right time.
"This was the moment where we manned up and said, 'We've done what we can with Westlife.'"
And the pop star reveals their manager, The X Factor judge Louis Walsh, has been left heartbroken by their decision: "He thought the idea of the split would go away when we told him. He finds it hard to talk about it.
"He hopes it'll be a long break but we've had to keep enforcing it to him, it's not. He's devastated."