The campaign financing tactics of Mexico's ruling Institutional Revolutionary Party are the stuff of legend.

The party has long been known to shake down tycoons for million-dollar donations. In 1993, 25 businessmen were asked to give $25 million apiece at a fancy dinner with then-President Carlos Salinas de Gortari.But now, for the first time, a bank scandal is giving the public a good look at how the ruling party helped create a class of business and banking tycoons and then benefited as they funneled some of their profits into its campaign coffers.

An unprecedented audit of the government's $55 billion bank-rescue fund by the opposition-led Congress has turned up evidence that financiers blamed for Mexico's banking crisis gave millions of dollars - it's unknown how many - to the ruling party.

The biggest donor, former banking and business magnate Carlos Cabal Peniche, is a fugitive from fraud charges and is believed to be living in Europe. Critics say the government doesn't really want to catch him and have him testify.

But two other men facing banking and business fraud charges have said they gave multimillion-dollar donations to the ruling party - and stuck taxpayers with the bill after the banking system collapsed.

It is unclear whether the donations broke any of Mexico's lax campaign-finance laws. But the revelation has sparked calls for the ruling party, popularly known as the PRI after its Spanish initials, to repay the money and for the government to adopt tighter campaign rules.

"We need a broad reform in campaign financing, through which a special agency . . . could investigate the sources of campaign funds," said Javier Coral, spokesman for the center-right National Action Party.

The PRI says it did nothing wrong and won't return the money.

"Political parties have the right to receive private donations . . . without any prejudgment about the donor's legal status," said the party's president, Mariano Palacios Alcocer.

The PRI finance secretary, Jose Luis Stein, said recently that the party would try to make its financing "more transparent" and that it would not accept private donations in 1998.

But there are few elections in 1998, so the party doesn't need such donations, and Stein said the PRI might accept donations in 1999 and 2000.

The disclosures about businessmen's donations have scandalized ordinary Mexicans, most of whom are too poor to even have bank accounts. They also are the ones who, under the government rescue plan, will pick up the $55 billion tab for the failed banks and bad loans left by the 1994 peso devaluation.

Angel Rodriguez, a former banker who faces tax evasion and fraud charges and who left most of his debts to be covered by the bank rescue fund, told lawmakers in August that he contributed millions of dollars to the PRI.

Gerardo de Prevoisin, a former Aero-mexico airlines executive, recently acknowledged in a U.S. court case that he withdrew $8 million from the airline to give to the ruling party. That money, along with the bankrupt airline's other debts, are to be paid off by the rescue fund.

Both men, like Cabal Peniche, rose to riches when the government converted state enterprises to private companies in the early 1990s.

PRI officials deny receiving money from Aeromexico, but acknowledge getting money from de Prevoisin.

Palacios Alcocer, the party president, noted the Federal Electoral Institute found no irregularities in PRI spending.

But the agency responded that it relies on spending reports submitted by political parties, then checks if funds were properly spent. It never thoroughly traces the sources of funds.