Roger Clemens is used to handling pressure as one of the greatest baseball pitchers of all time. But the former New York Yankees player came under greater scrutiny yesterday than he ever has on the pitcher's mound.

The burly sports star clashed in a televised congressional hearing with the former trainer who claims that he used steroids and human growth hormone (HGH) to boost his performance.

The showdown was as intensely watched as any pitching duel in a World Series game. Clemens and his accuser, Brian McNamee, each gave sworn testimony that directly contradicted each other. “Let me be clear, I have never taken steroids or HGH,” Clemens told the House Committee on Oversight and Government Reform.

Mr McNamee replied: “I injected those drugs into the body of Roger Clemens at his direction. Unfortunately, Roger has denied this and led a full-court attack on my credibility.”

The accounts will expose one of them to possible perjury charges for lying to Congress under oath. “Someone isn't telling the truth,” Henry Waxman, the committee chairman, said. “If Mr McNamee is lying, then he is acting inexcusably and has made Mr Clemens an innocent victim. If Mr Clemens is not telling the truth, he is acting shamefully and has smeared Mr McNamee. I do not think there is anything in between.”

The hearing was the climax of a 20-month investigation by the former Senate Majority Leader, George Mitchell, that found widespread use of performance-enhancing drugs in America's national sport. He began the inquiry after revelations in the book Game of Shadows by Barry Bonds, who holds the record for hitting home runs.

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