Speaking on ITV1 show The Truth About Boybands, Nigel admitted that he regrets not showing Robbie how much he appreciated the work that he put into the group.
"Robbie was my favourite because Robbie just wanted to perform," he explained. "If Robbie had ever come to me and said, 'Nigel, help.' Or, 'I'm having a problem with something,' I would have done it.
"If I had to do it all again, I'd do everything exactly the same, because I think it was all perfect. The only thing, personally, that I would do is spend a bit more time telling them how much I love them - which is probably what I didn't do, certainly in Robbie's case. I think that's where I went wrong."
Robbie fell out with Nigel before leaving Take That in 1995. In his 2004 autobiography Feel, the singer accused Martin-Smith of destroying his confidence during his time in the band. Last year, he was forced to remove insulting lyrics about Nigel from his Rudebox album.
The Truth About Boybands airs on ITV1 at 9.40pm tonight.