Take That will reunite on the 'Let It Shine' finale.
Robbie Williams is set to join bandmates Mark Owen, Gary Barlow and Howard Donald on the show, which is seeking to find performers to play a fictional boyband in Gary's West End musical, 'The Band' and he decided to get the band together for the final show.
However, he reportedly did not ask Jason Orange, who quit the group in 2014, if he wanted to take part.
A source told The Sun on Sunday: "Gary wanted to finish off 'Let It Shine' with a bang and he thought a Take That reunion to close the show was the perfect way to achieve it.
"The idea is that it would also set the stage nicely for the musical to follow.
"Robbie seems very keen to get on board, so things are looking good. But in the end, Gary decided not to even ask Jason.
"He felt the chances of him doing it were so non-existent that it wasn't worth the effort.
"Jason just isn't interested now, he has his own life away from Take That.
"With him out of the picture, Gary is pouring his energy into making sure their reunion as a four-piece is a huge success and blows the audience away."
Meanwhile, 'Let It Shine' contestant Callum Howells has quit the show after landing a high-profile West End role.
The 17-year-old actor and singer was cast in 'She Loves You' at London's Menier Chocolate Factory, and opted to leave the TV show.