Bell, who was removed from the closer role after struggling earlier this season, made the comments on "The Dan Sileo Show" on 560 WQAM in Miami.
"It's hard to respect a guy that doesn't tell you the truth or doesn't tell you face-to-face," Bell said. "There's probably reasons why."
Bell, 34, has a 5.19 ERA and has converted just 19 of 26 save opportunities this season, his first since signing a three-year, $27 million contract with the Marlins.
Bell has posted a 3.12 ERA since the demotion from the closer role but said that Guillen has not given him the opportunity to reclaim the job.
"I stunk in April, plain and simple," Bell said. "I said I stunk, I worked hard, I busted my butt. I think I've had a tremendous second half. I'm not closing -- I know that. But I just kept my mouth shut because I want to regain what I had, and I feel like I can't do that."
Bell attempted to clarify his comments Tuesday during a different interview with MLB Network Radio, claiming that he did not criticize Guillen.
"I was never criticizing Ozzie," Bell said. "I don't think that's what I was doing on the radio. I was choosing my words kind of right. Apparently, I didn't get it too right, but the thing is I respect Ozzie as a manager."
The last-place Marlins own a 66-87 record in Guillen's first season with the franchise. Bell accepted part of the blame for the Marlins' disappointing performance during his interview Tuesday, also acknowledging that he should not have made his comments Monday on WQAM.
"I don't think Ozzie's the reason why we really stunk this year," he said Tuesday. "I think ... me not performing to the next guy not performing, that's the reason we didn't win this year. It's not because of Ozzie. It's getting totally blown out of proportion for the simple fact (that) everybody's looking for a scapegoat. Everybody's trying to point at Ozzie or somebody in this organization. ... I just think everybody's trying to point fingers why we didn't win. And did I say something I probably shouldn't have? Yes, I did. I'm going to own up to it."
Bell initially declined to comment directly about Guillen during Monday's interview, saying only, "it's been an interesting year with Ozzie."
But although he did not state Guillen's name, Bell eventually offered harsh criticism, presumably directed at the mercurial manager.
"It's just one of those things that -- what you see is what you get," Bell said. "I'm not going to be two-faced. I'm not going to sneak around your back and say this and that."
Monday's interview came one day after Guillen told Fox Sports Florida that he defends his decision to replace Bell with Steve Cishek. But Guillen also told the website that Bell would be given the opportunity to close again in 2013.
Guillen also made headlines on Friday when he made public comments that reportedly angered Marlins owner Jeffrey Loria.
"If Jeffrey doesn't think I'm doing the job I should do ... it's not the first time he's fired a manager," Guillen told reporters Friday in New York. "Look yourself in the mirror and ask why so many (expletive) managers come through here."