Mr Fiske's replacement is Kenneth Starr, 47, a Republican lawyer who served as solicitor-general under President George Bush. He was appointed by a panel of three senior appeal judges after re- enactment of the independent counsel law which had lapsed in 1993.
The news, which took Washington by surprise, came just as the first round of Whitewater hearings ended on Capitol Hill.
Mr Fiske had been appointed by the Attorney-General, Janet Reno, earlier this year. But despite apparently solid Republican credentials, he was increasingly attacked by senior Republicans as too sympathetic to the Clinton White House, and hostile to congressional efforts to investigate Whitewater.
At Mr Fiske's insistence, the Senate and House have had to confine their questioning to matters already dealt with in his published reports. The purpose was to avoid interferences with the judicial process of the kind which allowed Colonel Oliver North to go free in the Iran Contra affair. But the effect has been to reduce the hearings, for the most part, to a rancorous repetition of facts already known.
The precise impact of Mr Starr's arrival was unclear last night but John Kerry, of Massachusetts, a senior member of the Senate Banking Committee, said it was bound to lengthen proceedings. That is unwelcome news for Mr Clinton.
It seemed unlikely last night Mr Starr would decide to re-open inquiries completed by Mr Fiske, in which he has cleared the White House of wrongdoing. Lately, however, Mr Fiske had been working on the Arkansas end of Whitewater. If Mr Starr starts the investigation again from scratch, Whitewater could prove a factor into the 1996 election year.