He told the East London club he wanted a move the day after they got relegated from the Premiership almost three years ago.
After first making a name for himself at Upton Park, Defoe has been vilified by supporters of his former club ever since his move to Spurs in January 2004, which served to intensify the rivalry among supporters of the two sides.
Now that Defoe has broken into the England squad, it upsets him that he cannot go and watch the Hammers play on his day off.
He said: "I played for Bournemouth and used to go back and watch them play and the fans were great, and I'd love to do the same at West Ham, but it is difficult and I regret the way I left."
Source: The People