The former Crystal Palace and QPR boss was approached by the Championship club to succeed Billy Davies, who was sacked on Monday following a poor run of form that culminated with Saturday's 5-0 loss to rivals Derby County.
Forest have slipped out of the play-offs after a return of just three points from seven matches and the vastly experienced Warnock had been touted as the man to turn their fortunes around.
However, the 65-year-old suggested that talks over the post had broken down.
"I felt that I have to do the job the way I see it being done," Warnock, who was most recently at Leeds United, told BBC Radio Nottingham.
"And I just couldn't totally see being able to do that, so it was difficult.
"It's been a hectic 48 hours. It's a great club. I said I wouldn't have come back (into the game) unless it was an opportunity to get success at a club.
"It couldn't have fitted the bill better with nine games - 12 including the play-offs - to get up.
"In the next 12 games it was a great possibility to get promoted. It got me excited but you have to look beyond that.
"The chairman (Fawaz Al Hasawi) is a lovely man. He loves the club. But I found it very difficult that there was nobody English around the club to speak to that had football experience. I felt it is area they need to look at.
"It's not knocking them because it's the way they do business. It's different cultures but it wasn't for me at this stage of my career. If I couldn't do it how I saw fit then I had better leave it."
A host of other names have been linked with the City Ground vacancy, including fans' favourite Stuart Pearce, who has been out of club management since leaving Manchester City in 2007.
