SAN FRANCISCO – Barry Bonds’ personal trainer wants to withdraw his guilty plea because prosecutors based their steroid distribution case on an illegal recording, his lawyer said Tuesday in a court hearing.

Greg Anderson, who is jailed for refusing to testify before a grand jury probing whether Bonds committed perjury, already served a three-month prison sentence after pleading guilty to the steroid charge.

But attorney Mark Geragos said Tuesday that an illegal tape recording of Anderson was the basis for the federal case against him in the Bay Area Laboratory Co-Operative scandal. A federal prosecutor acknowledged having a tape of Anderson discussing Bonds and undetectable performance-enhancing drugs at least a month before the trainer’s guilty plea last year, but said Geragos’ claims were “ludicrous and speculative.”

“That’s speculation by Mr. Geragos. He’s wrong,” said Assistant U.S. Attorney Jeff Nedrow.

The claim was the latest effort by Geragos to get a federal judge to free Anderson, who is being held for refusing to testify before a grand jury investigating whether Bonds lied when he told a grand jury in 2003 that he never knowingly used steroids.

Anderson served three months in prison and three months of home confinement after pleading guilty to distributing steroids and laundering money in the BALCO case. He served 15 days in prison in July for refusing to testify to a grand jury about Bonds, and was jailed again Aug. 28 for refusing to testify before a new grand jury.

Authorities have refused to release the tape to Anderson. Nedrow maintained Tuesday that the recording was legal and said he first learned of it in 2004 from the San Francisco Chronicle.

Nedrow said prosecutors didn’t get access to the tape until a month before Anderson’s plea deal. But Geragos suspects investigators had it all along and used the tape as an illegal roadmap to build a case against Anderson.

It has not been publicly revealed who made the recording. The government said the recording was made of a face-to-face conversation, while Anderson suspects it was made of a telephone call.

On the tape, according to the Chronicle, Anderson said: “The whole thing is, everything I’ve been doing, it’s all undetectable. The stuff I have, we created it. You can’t buy it anywhere else, you can’t get it anywhere else.”

Four other men also have pleaded guilty in the BALCO scandal for participating in the distribution or manufacturing of undetectable steroids to elite athletes.

Geragos said authorities only recently revealed the tape so they could build a perjury case against Bonds.

“The strategy is a perjury trap, obviously,” Geragos said.

Geragos did not say when he would seek to withdraw Anderson’s plea.