The Bulgarian, who is now playing for Fulham, joined United from Tottenham Hotspur in 2008 and went on to net over 50 goals for the Red Devils.
However, the forward was often criticised by fans for having an idle playing style, a judgement that he disagrees with.
"I left Manchester United with my head held very high," the 31-year-old told The Sun.
"I gave 100% and no-one could doubt my performances, especially when you compare how many minutes I actually played.
"I was the Premier League's top goalscorer in 2010-11 and never wanted to be on the bench."
Berbatov has scored three goals in seven appearances since joining the Cottagers.