Robbie Williams has described 'Rudebox' as the "biggest regret" of his career.

The 'Let Me Entertain You' hitmaker left his fans totally baffled with his 2006 single, which ditched his famous pop rock sound for more of a hip hop and dance influence, while the lyrics referenced Adidas Superstars, "pockets full of Durex" and questionable rhymes.

Reflecting on the song - the title track from his seventh solo album - he told NME: "My biggest regret is putting that out as the first single.

"If I’d have put it out third and explained properly [that] it’s daft – I know! I’m not trying to be a grime artist. I know it’s daft."

He confessed that mortifying moment in his upcoming four part Netflix documentary is seeing himself hyping up the song to his fans.

He added: “In the documentary, the biggest cringe point for me is explaining to an audience who are about to listen to ‘Rudebox’ for the first time that this is gonna be the biggest single since ‘Angels’.

"Then I had another thought about it, that it’s my second most important single because ‘Angels’ gave me the career and ‘Rudebox’ heralded the end of my imperial phase.

"So in a way I was right, but not in the way I wanted to be.”

The 49-year-old pop star is seen reliving his past by watching old videos in new Netflix series 'Robbie Williams' which covers his rise to fame, career in Take That and his solo success as well as his issues with addiction and mental health battles.

Director Joe Pearlman recently revealed looking back on the darker aspects of his life often proved too much for the singer.

Joe told The Independent newspaper: "He was going to have to rewatch active addiction: I think we knew that was going to be incredibly challenging and also potentially triggering.

"So we had to be very careful around those moments ... This thing would take its toll on a person. And there were times when we couldn’t continue, times when we had to call it [off] and that was fine."