Speaking on Canada's 'George Stroumboulopoulos Tonight', he explained: "Actually I had this argument with Adele, which is probably the most ridiculous thing I've ever said. I was saying, 'You know, you can really just like reach for it,' and she was like, 'You do realize I am like the biggest-selling female artist ever?'
"And I just for some reason just decided to get into an argument with her.
"I woke up the next day really regretting the whole thing."
Robert - who is dating his 'Twilight Saga' co-star Kristen Stewart - also claimed his vast fame hasn't stopped him from meeting new people because he isn't very sociable anyway.
"I have this fantasy that if I wasn't famous I'd be out meeting random people on the street but that's not true. Most of the time you try to avoid random people on the street whether you're famous or not."