Roger Clemens, the superstar baseball pitcher, told a congressional committee under oath on Wednesday that he never used performance-enhancing drugs and called his chief accuser, who claims to have repeatedly injected Mr Clemens with the drugs, a liar.

“I have never used steroids, human growth hormone, or any other type of illegal performance-enhancing drugs,’’ Mr Clemens said in his opening statement at the hearing. “I think these types of drugs should play no role in athletics at any level.”