MEXICO CITY, Nov 10 (Reuters) - Stung by a string of ballot-box
                  defeats, Mexico's conservative opposition issued an unusually harsh rebuke
                  of the ruling party on Monday, accusing it of resorting to old habits of
                  electoral fraud that threatened the key 2000 presidential vote.

                  A day after getting shut out in three gubernatorial races, the National Action
                  Party (PAN) accused the Institutional Revolutionary Party (PRI), in power
                  since 1929, of massive vote buying to win several key state contests so far
                  this year.

                  The PAN, normally seen as conciliatory, promised a national campaign of
                  protest against the alleged electoral trickery and said its lawmakers would
                  immediately introduce legislation for campaign finance reform.

                  "We are indignant at ... the corruption of the electoral process through vote
                  buying ... and the illegal participation of state and city governments in
                  diverting material, financial and human help ... in favour of the PRI," the party
                  said in a statement late on Monday.

                  "In the midst of our already painful inequalities, this is simply criminal."

                  Calls by Reuters to PRI headquarters in Mexico City for a response to the
                  allegations went unanswered.

                  The PAN lost state races on Sunday in Puebla and Sinaloa, where the PRI
                  won handily, and in Tlaxcala, where the leftist Party of the Democratic
                  Revolution (PRD) pulled off an upset for only its second gubernatorial post
                  in history.

                  But the party said that despite its own electoral mistakes, the PRI helped
                  itself by using public money and material to help local candidates, a move it
                  said jeopardised upcoming national elections in 2000.

                  "Since elections in Yucatan (state) earlier this year, until these most recent
                  races .... we have seen the reemergence of a rebellious attitude similar to
                  those by governments which want to turn back the clock on democratic
                  advance," it said.

                  "Along with millions of Mexicans, we ask the PRI and its government
                  whether this authoritarian regression is a national policy or uncontrollable
                  outbreaks of local party power. Either prospect is chilling ahead of the 2000
                  race," the party said.

                  The 2000 presidential race promises to be Mexico's biggest electoral
                  showdown of the century. The PAN and PRD both believe they will finally
                  be able to oust the PRI from power it has held through means both fair and
                  foul since 1929. The PAN and PRD now govern a vast majority of
                  Mexicans at the local level.

                  Ironically, the PAN has sometimes been a key PRI ally on economic reform
                  issues and has rarely been vocal about allegations of vote rigging, painting
                  the leftist PRD as a violent party for its pitched protests against past
                  episodes of real or imagined PRI electoral fraud.

                  But the party has been taking a tougher line recently after winning just one of
                  several state races this year and losing a key governorship it already held in
                  the northern border state of Chihuahua.

                  Party leaders also said on Monday that a solution was still far off to a
                  long-running dispute over a $65 billion bank bailout bill from Mexico's
                  1994-95 peso crisis. Foreign investors have keenly awaited a solution to the
                  controversy.

                   Copyright 1998 Reuters.