Pitching great Roger Clemens joined home-run king Barry Bonds among dozens of Major League Baseball players named on Thursday in the Mitchell Report that detailed widespread use of banned drugs in America's pastime.

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The sharply worded report by former US Senator George Mitchell called for unannounced year-round testing by an independent body to help end a pervasive culture of performance-enhancing drug use among all 30 big-league teams.

It blasted baseball ownership for overlooking the problem and the players' union's resistance to drug testing in the past for creating an environment that allowed drug cheating and cast doubt over some of the sport's most cherished records.

Players named for using steroids included a virtual Hall of Fame of some of the sport's biggest stars of recent years: Clemens, Bonds, Andy Pettitte, Jason Giambi, Gary Sheffield, Eric Gagne and Miguel Tejada.

Bonds, who set the single-season home run record of 73 in 2001 and this past season eclipsed Hank Aaron as baseball's all-time home run king, is facing trial on federal charges he lied to a grand jury in denying he used steroids.

Clemens, a seven-time winner of the Cy Young Award as best pitcher, angrily denied allegations in the Mitchell Report. Clemens, 45, pitched for the New York Yankees this past season.

Mitchell's 311-page report said it did not think players cited should be punished, given that many of the findings involved activities dating back almost a decade and before Major League Baseball and the Players' Association agreed in 2002 to drug testing.

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Major League Baseball Commissioner Bud Selig, who commissioned the report, told a news conference he would act on the recommendations.

Selig said he reserved the right to discipline active players named in the report.

"I'm going to review his findings and the factual support," he said. "Punishments will be taken on a case-by-case basis."

'WIDESPREAD'

In his news conference, Mitchell said, "For more than a decade there has been widespread illegal use of anabolic steroids and other performance-enhancing substances by players in Major League Baseball in violation of federal law and baseball policy.

"The response by baseball was slow to develop and was initially ineffective," said Mitchell, a former US Senate majority leader, who launched the independent probe into doping in baseball in March 2006.

The report drew heavily on testimony from a former New York Mets clubhouse attendant who cooperated as part of a plea deal with federal officials after his arrest for distributing drugs.

Major League Baseball Players Association chief Donald Fehr said players may have been treated unfairly by the report.

"Many players were named. Their reputations have been adversely affected, probably forever, even if it turns out down the road that they should not have been named," he told a news conference.

"Anyone interested in fairly assessing allegations against the players should consider the nature of the evidence presented, the reliability of the source."

The biggest shock in the report involved detailed allegations by Clemens' personal trainer, Brian McNamee, of steroid use by the pitcher.

A lawyer for Clemens issued a statement saying he was outraged his name was included in the report.

VEHEMENT DENIAL

"Roger has been repeatedly tested for these substances and he has never tested positive," attorney Rusty Hardin said.

"Roger Clemens adamantly, vehemently or whatever adjective can be used, denies he has ever used steroids or whatever the word is for improper substance."

Mitchell said that since the start of steroids testing, the use of Human Growth Hormone has risen because, unlike steroids, it is not detectable through urine testing.

Mitchell said former baseball Commissioner Fay Vincent told him the problem was possibly "the most serious challenge that baseball has faced since the 1919 Black Sox scandal" -- when Chicago White Sox players conspired with gamblers to affect the outcome of the World Series.

The investigation linked more than 50 players to performance-enhancing drugs who had not been previously associated with doping and also named 24 others who had been previously cited in press reports and by the BALCO probe.

"It is a sad, sad day for the national pastime and all who love America," U.S. Anti-Doping Agency chief Travis Tygart told Reuters. "All involved should be ashamed."

Two US congressmen who held a 2005 hearing on steroids in baseball that rattled the sport said they planned to invite Mitchell, Selig and Fehr to another hearing next Tuesday.