The `Angels` singer has admitted he found it hard to forgive the Take That songwriter when he left the band in 1995 and even after seeing his former friend struggle to establish a solo career following the demise of the group, he couldn`t let go of his bitter feelings.
Robbie - who has now ended his feud with Gary and rejoined the group for a new LP and tour - said: "My problem has always been with Gary. It was always with Gary. I wanted to crush him. I wanted to crush the memory of the band - and I didn`t let go.
"You know, even when he was down, I didn`t let go. And for that I sincerely apologise."
Meanwhile, Gary has admitted he begged his bank to change the name on his credit cards after his career flopped while Robbie`s took off because he couldn`t take anymore ridicule.
He said: "It was hard watching Rob get further and further into the distance and I just seemed like I`d gone 10 steps back.
"It was a constantly daily mock. It followed me everywhere. You just seem like a total loser.
"In fact, I remember asking the bank whether I could change my name on my card. I couldn`t face my own name because even over the phone people would make some wisecrack."
Though Take That - also comprising of Howard Donald, Mark Owen and Jason Orange - are preparing to release their first album as a five-piece in 15 years and will embark on a mammoth European tour next year, their reunion was thrown into doubt after Robbie again quit the group last November following a brief appearance together, saying he wasn`t ready.
He explains in new documentary `Take That: Look Back, Don`t Stare`: "I wasn`t very well, physically. I just didn`t feel as if I had the energy to do it.
"It was a scary prospect to be out there among something so huge feeling depleted of life force."
Though he was eventually talked round by Mark, Jason was furious with the `No Regrets` singer`s actions.
He said: "It was like the rug was pulled from under my feet. I was gutted. I actually said to Rob, -Your whims have a direct effect on us.- "
`Take That: Look Back, Don`t Stare` airs in the UK on ITV1 on Saturday (13.11.10) night.