At the centre of the inquiry is a conflict between sworn denials of an affair from both Mr Clinton and Ms Lewinsky, and tape-recordings of conversations in which Ms Lewinsky appears to confirm it. Her lawyer has been negotiating for her to be given immunity from prosecution for perjury if she retracts her denial. The account she has offered so far - reported to be a confession of an affair but no confirmation that Mr Clinton tried to persuade her to lie about it - is said to be insufficient for Mr Starr to grant immunity.
Yesterday, the Washington Post printed a passage, said to be taken from Ms Lewinsky's account, which treads on the delicate ground between lying and not telling the truth. "Sources" are quoted as saying that Ms Lewinsky had asserted that she was not urged to lie, only to "tell a certain version of events - one that did not happen".
This detail coincided with new evidence that someone may have witnessed the President and Ms Lewinsky in compromising circumstances. The Wall Street Journal reported that a White House steward with access to the Oval office had testified that he had seen the two alone together in Mr Clinton's private study and had then found "tissues smeared with lipstick and other stains". The steward's lawyer immediately denied that this information had been contained in his client's testimony.
An earlier report that a member of Mr Clinton's secret service detail had caught the two in an intimate encounter was retracted by the Dallas Morning News, which said the second-hand account was "ambiguous".
The White House, meanwhile, continued to keep silent about the alleged affair and would not comment on reports that Mr Clinton was considering invoking "executive privilege". This permits a President to stop certain information getting into the legal or public domain so as not to jeopardise the relationship of trust between him and his advisers.