The 'Glad you Came' hit-makers ditched a ''great'' track penned by the 19-year-old pop sensation for their third studio album because it did not suit their ''mature'' sound.
Band member Max George told MTV News: ''We did a song with Justin. I think it was a great song and he did an amazing job writing it, but I think it was very much more suited to his style.''
The group - which also includes Jay McGuiness, Siva Kaneswaran, Nathan Sykes and Tom Parker - claim the long delays in releasing their new album, 'Word Of Mouth', has been because they have been creating the perfect sound.
Siva Kaneswaran said: ''I think that we weren't ready a year ago. It just wasn't ready; the songs weren't finished.
''We want to put out the best us and we are ready now and every song is so personal and we've all aged as writers, and it's very mature ... and it's the best album yet.''
The boys' busy schedule has also seen the second series of their E! reality show 'The Wanted Life' put on hold, but despite the two-year wait since 2011 album 'Battleground' the boy band claim it will be worth it when 'Word of Mouth' is released on November 4.
Jay explained: ''We had a very busy year. We decided to do a TV program [E!'s 'The Wanted Life'], which took up a lot more schedule then we thought, and then all this stuff that we planned to do kinda had to move back as well.
''And then we thought the album was good to go, and last minute a few quite cool gigs and a couple other things popped up that we thought, 'It's probably worth waiting for the album a little,' I mean, the fans have waited a few years, so what's a couple of weeks?''
The BBC drama starring Aidan Turner returns to BBC One on September 4th.