The singer, 36, told The News of the World how he drank a cocktail containing the drug – which comes from cactus – during a wild session in Ibiza in the 90s. It left him unfit for the following day's recording session with the rest of his band, Take That.
He said, 'I wasn't going to do any drugs because I had to be back at Gary Barlow's house the next day.
'But I drank these drinks called Poco Locos, at 30 quid a glass, which had mescaline, acid, and ecstasy in them.
'I had to catch a plane early in the morning, totally and utterly off my head. I got to Gary Barlow's house and everybody was waiting for me.
'I went in and I put my hands up and went, 'I've found God!' Then I collapsed and went to sleep for 48 hours in his bed.'
It was not long after that lead singer Gary fell out with Robbie, signalling the beginning of the end for the group that time around.