Mexico's political scandal over a fugitive banker's assertion that he gave $25 million to the ruling party's 1994 election campaign, including $5 million to President Ernesto Zedillo's campaign fund, is heating up rapidly.

The two largest opposition parties, the center-left Democratic Revolutionary Party (PRD) and the center-right National Action Party (PAN), asked Mexico's Federal Electoral Tribunal to reopen an investigation into contributions to the ruling Institutional Revolutionary Party (PRI), while leading opposition politicians are demanding the appointment of a special prosecutor to look into the banker's contributions.

The opposition demands came after a May 29 story in the Miami Herald that quoted fugitive banker Carlos Cabal Peniche as saying he had contributed $25 million to the PRI for the 1994 campaign. That would far exceed the officially declared campaign expenditures of the party, opposition leaders say.

Cabal Peniche, who was arrested in Melbourne, Australia, in November and is fighting an extradition request from Mexico, said he delivered $15 million to the campaign of the late Luis Donaldo Colosio, $5 million to Zedillo after Colosio's assassination in March 1994 and $5 million to Roberto Madrazo, the governor of Tabasco state.

Zedillo's spokesman, Fernando Lerdo de Tejada, sent a two-page letter to the Herald tonight stating that Zedillo had no knowledge of any contribution by Cabal Peniche to either his own campaign or Colosio's.