Mr O'Neill is the principle figure behind the Red Knight's Group, a consortium that this week announced plans to try to buy Manchester United from the Glazers.
Related ArticlesThe 'richest' football clubs in the worldDavid Gill launches fierce attack on Red KnightsRed Knights to target debt in bid for UnitedProfile: 'Red Knight' Jim O'NeillRed Knights want fans' support'Red Knights' plot £1bn takeover at Man UnitedGoldman Sachs was one of the underwriters of the club's recent £507m bond issue, earning a share of £15m in fees, and the family was outraged when Mr O'Neill criticised their heavily-leveraged ownership model shortly after the bond closed.
Asked for his opinion of the bond at the end of January Mr O'Neill said: "There's too much leverage going on with Manchester United, it's not a good thing, I'm not a buyer of the bond. I value my long-term support for Manchester United."
The Glazers were so incensed at Mr O'Neill's intervention that they complained directly to Mr Blankfein. His response is not known, but Mr O'Neill has not backed off from his view of the Glazers.
Goldman Sachs declined to comment.