The Bulgarian striker, who moved to Fulham on transfer deadline day on Friday, said he was unhappy with the way the United manager had treated him in the final months of his four-year stay at Old Trafford.
"I don't think I deserved such treatment at United -- not playing (regularly) in the last year," Berbatov told a news conference at Bulgaria's Vasil Levski national stadium in Sofia.
"I went more than 10, probably 15, times to ask the coach if they need me. And every time I was told that I'm an important player and should not leave, but then again I was not in the team.
"Maybe I should've gone when he (Ferguson) left me out of the squad for the Champions League final (in 2011). I know he's the boss, but he has lost, to some extent, my respect because of the way he treated me."
Berbatov became United's most expensive player when he joined from Tottenham Hotspur in 2008 for £30.75 million pounds, and was the Premier League's joint top-scorer in the 2010-2011 season with 20 goals.
The player's agent, Emil Danchev, said on Monday that Berbatov had received a late offer from Spurs at the end of the transfer window. "We were in touch with Tottenham at the last moment," Danchev said, adding that 12 clubs wanted to sign the striker.
Berbatov, who on Monday confounded expectations in Bulgaria that he would come out of international retirement, said he fell victim to a change in United's style of play.
"He (Ferguson) tried to explain to me that the team will be using a more direct style, with more speed," he said. "But I've never been among the fastest players, I like to hold the ball, this is my style.
"I found it hard to accept his decision (not to play him) - I still have my dignity. I scored many goals, I won the league two times, and I was the league top scorer, so it's not bad.
"I'll have no problems playing against United as this already happened in my career. But there's no point to look back again. I said goodbye to the people, who deserve it. I couldn't say goodbye to Ferguson."
Berbatov's transfer to Fulham proved controversial in Italy, as he twice turned down offers from Serie A clubs at the last minute to stay in the Premier League.
Berbatov denied he had acted inappropriately in his dealings with Fiorentina and Juventus.
"I've never personally told them, 'Yes, I'll play for you'," he said. "It's not my problem that someone is disappointed. After all, I choose where to play and be happy."
The 31-year-old angered Fiorentina when he turned his back on them last Thursday, one day before the end of the transfer window. The player then rejected the chance to move to Italian champions Juve.
"He did not deserve our city and our shirt and the values it represents," Fiorentina said in a statement.
Berbatov said: "It's stressful. One club called, then another, and a third, and then another. A man can go crazy at one point. I'm a human being and it's normal for me to hesitate."
Berbatov was in Sofia ahead of Bulgaria's 2014 World Cup qualifying game against Italy on Friday. He was called up for his country's qualifiers against Italy and Armenia but insisted he would not return to the national side.
"(Coach) Luboslav Penev was the only one who made everything possible to make me feel welcome, so that I can see that he wants me back," he said.
"We met at least twice, as friends. We discussed it but at the end of the day, the choice I made in the past still stands."
Berbatov, Bulgaria's all-time leading scorer with 48 goals, quit the team in 2010 hinting that fatigue and family commitments were behind the decision.