Robert Ray's comments are, however, certain to be seized upon by Mrs Clinton's opponents.
The independent prosecutor investigating the Clinton White House says he has found substantial evidence that Hillary Clinton was involved in several controversial sackings in the White House travel office in 1993.
However, Robert Ray says he doesn't plan to bring charges against the first lady because he can't prove that she deliberately lied about her role.
Mrs Clinton has always denied any involvement in the firings.
The announcement comes while she is busy campaigning to become a senator for New York in the elections in six months' time.
Dogged by controversy
Hillary Clinton has declined to comment on the independent prosecutor's finding of substantial evidence that she played a part in what has become known as "Travelgate".
Robert Ray's comments are, however, certain to be seized upon by Mrs Clinton's opponents.
Seven people lost their jobs in the office that handles travel arrangements for presidential trips in 1993.
And the sackings provoked one of several big controversies which have dogged President Clinton and the First Lady.
Robert Ray accused the White House of putting up substantial resistence to his investigators.
But he said he wouldn't be bringing charges against the First Lady because he couldn't prove conclusively that she lied about the affair.
Whitewater
This announcement is part of the gradual winding-up of the long-running Whitewater investigation, which has overshadowed the Clinton presidency.
It's been going on for seven years already, at a cost of $50m so far, and it reached its height in 1998 with the impeachment of the president over the Monica Lewinsky affair.
But there's still potential trouble ahead.
A couple of months ago, Robert Ray said he was actively considering bringing criminal charges against President Clinton when he ends his term in office next January.