St-Pierre said Tuesday a lack of strenuous drug testing was one of the factors that led to his decision to step away from the sport.
"It bothered me greatly, it was one of the reasons I decided to step aside," St-Pierre said Tuesday.
He vacated his welterweight title and took a hiatus from the sport in December, citing a need to lead a normal life and deal with mental fatigue.
The 32-year-old confirmed when asked by a reporter that his employer, the UFC, did not support him when he proposed drug testing in the weeks preceding his Nov. 16 fight against Johnny Hendricks.
St-Pierre stepped away following UFC 167 where he won a controversial split decision over Hendricks. After that fight, he said he needed time away to sort out some personal issues.
The star fighter was prudent in his comments Tuesday, being careful not to point fingers at any one person or fighter. He stressed he wasn't accusing anyone of steroid abuse.
St-Pierre said he wanted to bring the sport he loves to "another level" of testing and help those who are honest in the sport.
"I tried to change things, and unfortunately, maybe for money reasons, maybe for image, they were not ready to do that," St-Pierre said. "I tried to (bring about) change in a very diplomatic way and it didn't work so it's unfortunate, but I believe it will happen sooner or later."
The former welterweight champion said he hasn't made a decision to retire and added he's in top physical condition and still trains regularly.
While he has remained vague about a comeback, St-Pierre says the break has made him a better fighter because he's not feeling any external pressure. He repeated he hasn't set any timetable to make a decision regarding his UFC future.
St-Pierre said implementing drug testing is not a condition for any potential return to the sport. He added he could understand the reticence from the organization — a failed drug test could dramatically change a card and result in people losing money.
St-Pierre was in Montreal handing out bursaries for athletic excellence.
"I feel very good, I feel very happy," St-Pierre said, appreciating a holiday season with his family and being able to have a few drinks.