The road cyclist and Scottish Commonwealth gold medal winner said going as the "black sheep" would not be a "joyful experience".
Millar, 35, was in 2004 suspended from cycling for two years after he admitted using the "blood-boosting" drug EPO. Now back at the top of the sport – and campaigning to prevent others making the same mistakes – he is still subject to a lifetime Olympic ban imposed by the British Olympic Association under its byelaw for those found guilty of taking performance-enhancing drugs.
WADA, the World Anti-Doping Agency, has declared the BOA non-compliant with global anti-doping rules. It claims Millar – and others, including sprinter Dwain Chambers – has served his suspension and that the BOA's policy amounts to a second sanction. The Court of Arbitration in Sport will rule on the matter early next month.
Speaking on a BBC Radio Scotland programme to be aired today, Millar said: "I'm not going to the Olympics. In all honesty it's something I signed off from a long time ago. I'm quite happy looking forward to 2014 in Glasgow and the Commonwealth Games. That will be a much more joyful experience than me going to the Olympics as a black sheep. Even if it did all go through, I don't know if it would be a very joyful experience for me."
He said that if the court ruling finds against the BOA lifetime ban, the London Olympics would be a "very difficult decision" for him.
He added: "Is it a stronger message if I don't go, or that I do go and perhaps try to change peoples' opinion that forgiveness should be offered? I've nailed myself to a few crosses and I'm not sure if I am willing to go for the final big one on this. I don't think it's part of my story being an Olympic champion. I think that's something that should have happened if I'd been born 10 years later. I missed that window. I think I'll leave it to the good guys."
Millar said he started doping in 2001, when he had a disastrous Tour de France. He said cyclists "flagrantly" took drugs, and got away with it because they were used for the training periods building up to the races, and not the races themselves, and were therefore "essentially undetectable".
He said taking drugs became "the difference between going to a race and hoping to win, and going to a race and guaranteeing to win".
He confessed after French police found two syringes in his Biarritz apartment. He added: "I'd already stopped doping, ironically, before I was found out and admitted everything, and yet I wasn't at peace with myself in the slightest. I was in a bit of a descending spiral of remorse and self-disgust. I do everything I can to prevent other people making the mistakes I made, and to help the younger guys have a cleaner sport to go in to."
Millar was widely expected to win two gold medals in Sydney in 2004. He also missed the 2008 Games in Beijing. He said: "It was hard watching 2004, when I saw one of my best friends, [the Australian] Stuart O'Grady, win. And 2008 was hard just seeing them all there."
"People make mistakes. Things should be punished but they should be forgiven, and given a second chance. We are human beings. Why do sportsmen and women get punished more harshly than people in the normal world? Isn't the human condition about forgiveness, learning, changing and developing as people?"
BOA chairman Lord Moynihan has defended the lifetime ban, saying: "I feel no anger towards David Millar; he's a remarkable athlete. I just feel a great deal of sadness that somebody who was not a young kid when he made the decision, but a mature athlete who was competing at the very top level, decided to take drugs to cheat his fellow athletes. He knew the price.
"In sport, the one thing you do not do is cheat. You know the consequences – you'll never be selected again. I'm very conscious of the issue of redemption, but where is the redemption for the clean athlete cheated out of selection by somebody who has taken performance-enhancing drugs? You never hear their names or the training they have done."
Olympic medal-winning rower Anna Watkins added: "I've read his book and it seems David Millar took drugs just when he was getting really good, so I don't necessarily want to be on an Olympic team with him. The team's been surveyed time and again, and the people actually going to the Olympics don't want people with drugs convictions standing shoulder to shoulder with them wearing the same jersey. We would like to be a British team that is clean and sets an example."
Cheats and Champions is on BBC Radio Scotland today at 2.05pm