(CBS/AP)SAN FRANCISCO - Federal prosecutors are asking a judge to send former Major League Baseball player Barry Bonds to prison for his April conviction for obstructing a grand jury investigating sports doping.

Court documents detail prosecutors are objecting to a recommendation by a federal probation officer that Bonds get only a probation when he's sentenced on Dec. 16.

The San Francisco Chronicle reports prosecutors recommended a 15-month prison sentence for the former San Francisco Giants' hitter saying he purposely gave misleading answers to a grand jury and evasive testimony about steroids.

The grand jury was investigating a laboratory that distributed performance-enhancing drugs to professional athletes. Prosecutors said in a filing to the judge who will sentence Bonds that his actions were part of a "calculated plan to obfuscate and distract the grand jury from getting to the truth."

They said too that Bonds' sworn claims that he did not take steroids and a human growth hormone were "patently false," even though a jury deadlocked on three charges that he had committed perjury.

"Bonds' pervasive efforts to testify falsely, to mislead the grand jury, to dodge questions, and to simply refuse to answer questions in the grand jury makes his conduct worthy of a significant jail sentence," prosecutors told U.S. District Judge Susan Illston.