The 'Bodies' hitmaker - who left the group in 1995 and embarked on a successful solo career - has revealed he has been meeting up with former bandmates Gary Barlow, Howard Donald, Jason Orange and Mark Owen to work on a secret project.
When asked if he'll be performing with the foursome again, he said: "We've got together, done bits and bobs. I can't say much, but yes, I hope so."
The 35-year-old singer - who has previously battled alcohol and drug addictions - also spoke candidly about how he was forced to stop performing in 2007 when his personal problems began to spiral out of control.
In an episode of TV talk show 'Friday Night With Jonathan Ross' due to air in the UK on Friday (06.11.09), he said: "The decision to quit playing live was made for me, I've always been very nervous... 80,000 people, it's an unnatural thing to do. You don't know what's going on in my head.
"It's traumatic, really scary. I ended up in rehab again, it was 'What are you doing to yourself?' I thought it's time to break the cycle."
Robbie is now determined to remain sober for his girlfriend of three years, Ayda Field, so they can start a family together.
He added: "I've taken the pressure off myself, it's a part-time thing these days. The missus keeps me grounded. There's no need to take myself out of my mind any more.
"I thought I was going to be a bachelor but I was introduced to Ayda and things just changed. She's a wonderful person and I'm in love. She's really broody and I'm getting there."
Robbie sparked speculation he was working with the group again after they were all spotted at New York's Electric Lady Studio while the band were in America for Mark's bachelor party.