Gary Barlow used to play "terrible" tricks on his former bandmate Robbie Williams.
The Take That star's rivalry with Robbie became so intense they resorted to dirty tactics to annoy each other after Robbie left the band.
He said: "Oh yeah. Me and Robbie used to play terrible tricks on each other.
I took Robbie's album back to a music shop once and...' Stupid, stupid things! Things you wouldn't dream of doing as a 37-year-old bloke. Quite seriously I'd do it, as well. It wouldn't be as a joke."
Gary, who was recently reunited with Robbie during a trip to Los Angeles, insists he doesn't harbour any bad feelings towards his old foe anymore.
He added: "I don't feel anything about Robbie now. I feel really good about what's happening with us, I feel good about it all - but not at Robbie's expense. Not at all."
Gary's bandmate Mark Owen admits his only regret about Take That reforming in 2005 was Robbie's absence from the group.
He told Britain's Observer Music Monthly magazine: "I would have loved for Robbie to have come and done it with us. He should be here, having a laugh.
"Originally I wanted him to come back so that we could make something right, something that had been wrong. Back in the past. But I think we've done that now. We saw him in Los Angeles. Really, all Take That is is a therapy session. One long therapy session."