More than 80 Republican Congressmen have asked the government's ethics office to investigate Mrs Clinton's stake in Valuepartners, a Little Rock investment group which took short positions in several health care stocks in early 1993 - in other words betting that the share prices would fall. The White House has denied any impropriety, saying that Hillary Clinton knew nothing of Valuepartners' activities after 1992.
But the Clinton's financial assets of around dollars 500,000 ( pounds 340,000) were not put into the automatic 'blind trust' customary for a Presidential family until July 1993.
The move increases the pressure on Mrs Clinton to explain publicly her involvement in the Whitewater controversy, a tangled skein that has not only enveloped the Clintons' links with the Whitewater real estate venture and the failed Madison Guaranty bank, but all their Arkansas financial dealings.
Yesterday there were signs of a change of heart by the White House. After a week of stonewalling and media criticism that Mrs Clinton, whose Whitewater role was greater than her husband's, was evading scrutiny, Officials are said to be considering a television appearance by the First Couple to take questions on Whitewater.
Though physically absent, Mrs Clinton was present in spirit at the yesterday's opening grand jury proceedings, in the same courthouse through which once trooped witnesses in the previous causes celebres of Watergate and Iran-Contra. Maggie Williams, her Chief of Staff, and her press secretary, Lisa Caputo, were the first of 10 subpoenaed White House and Treasury officials to be questioned by special counsel, Robert Fiske.
Ms Williams helped the White House counsel, Bernard Nussbaum, remove Whitewater documents from the office of Vince Foster, a close friend of the Clintons and Mr Nussbaum's deputy until his apparent suicide last July.
Mr Foster's death has been an enduring mystery and source of rumours. Whether Ms William's testimony yesterday covered the episode in Mr Foster's office was unclear. But it did deal with the meetings between White House and Treasury officials on the progress of a federal probe into Madison's failure. Ms Williams took part in one of the sessions, last month. Their disclosure a week ago transformed an Arkansas financial imbroglio into a full- fledged White House scandal. A key issue is to what extent she informed, or was instructed by, Mrs Clinton.
For all the media uproar, the public is still unconvinced by Whitewater. According to one poll, only 16 per cent think the President did something illegal, compared to 34 per cent who consider Whitewater little more than Republican mischiefmaking. But the positive ratings of both Clintons has slipped from 55 per cent to below 50 per cent.