The controversy over Mr. Provopoulos and the Greek bank bailouts echoes the public discontent over the taxpayer-financed rescues of large American banks during the financial crisis that began in 2008. Five years ago, Henry M. Paulson Jr., the former Goldman Sachs chief who was then Treasury secretary, and others with ties to Wall Street orchestrated those bailouts, prompting a public outcry.

In Greece, Mr. Provopoulos fast-tracked a slate of deals that transformed Piraeus Bank, where he had been a vice chairman before joining the central bank, into the nation’s most powerful bank. The legal saga is also a visible sign of a behind-the-scenes power struggle between Mr. Provopoulos and the government of Prime Minister Antonis Samaras over control of the country’s banks, which for decades have been a source of patronage and influence in Greece.

Whether prosecutors will formally charge Mr. Provopoulos is unclear. Mr. Lavrentiadis’s lawyers have argued that their client’s case and that of Mr. Provopoulos must be investigated together, as Mr. Kaloudis suggested in his report.

The governor’s supporters say that the inquiry is politically motivated and baseless, an attempt to force out Mr. Provopoulos so that the largely discredited political class can reassert itself. But Mr. Provopoulos’s critics argue that the playbook used in the Proton deal — described as a series of back-room maneuverings that rewarded Michalis G. Sallas, the domineering chairman of Piraeus Bank — was deployed repeatedly, most recently when Piraeus bought the Greek operations of three Cypriot banks last March at a knockdown price of 524 million euros, and a few months later booked a profit of 3.5 billion euros on the transaction.

“The position of the governor has become very strong, and I do not think that he has been subjected to proper scrutiny,” said Pavlos Eleftheriadis, a law professor at Oxford University who has been critical of how special interest groups in Greece have expanded their influence and power in recent years. “There was the spectacular failure of Proton, and there are questions about the Piraeus deal in Cyprus. We need root and branch reform of all our institutions — including the Bank of Greece.”

It is not hard to see why Mr. Provopoulos has become a lightning rod. He has done little to disguise his low regard for the political establishment, openly criticizing its fiscal policies and privately upbraiding both the conservative New Democracy party and the left-leaning Pasok party for not attacking Greece’s economic problems with more force and speed.

“I am not in this job to please politicians,” Mr. Provopoulos, 63, said in an interview here in his capacious office. “I am not just an ordinary citizen. I have much larger responsibilities. My actions will be judged in the future after the dust has settled and people are in a better position to assess the results.”