A court in Rome has summoned Bank of Italy officials for questioning on the state bailout of Monte dei Paschi, as scandal spread over the trading that plunged the world's oldest bank into trouble.
The Tuscan bank suffered a further blow on Thursday when the Standard & Poor's agency cut its long-term credit rating deeper into "junk" territory.
The Lazio regional administrative court said in a statement that it had called Deputy Governor Fabrizio Saccomanni and Luigi Federico Signorini, the official in charge of bank supervision, to a hearing on Saturday. The central bank said they would not attend, but would be represented by counsel.
The Bank of Italy, led at the time by Mario Draghi who has gone on to head the European Central Bank, faces criticism of its supervision of the 540-year-old institution from Siena and of its role in approving a government bailout last week.
(Read More: Draghi's New Powers Under Monte Paschi Spotlight)
The summons to the central bankers follows a request to the court by consumer lobby Codacons to block the 3.9-billion euro ($5.3 billion) state loan approved by the Bank on Saturday.
Monte dei Paschi was left facing losses of 720 million euros ($977 million) on a series of derivative and structured finance transactions. Already badly weakened by paying 9 billion euros cash for rival Antonveneta just before the 2008 global crash, the trades appear to have been made to hide losses on that deal.
Standard & Poor's, which relegated Monte dei Paschi to junk status last December, cut its long-term credit rating on Thursday by one more notch to "BB". The agency cited concerns over potential losses from structured finance contracts, which it said revealed a risk of management weaknesses.
Regulators including the Bank of Italy are under pressure over their failure to head off the problems, despite repeated warnings dating back to at least 2009 that Monte dei Paschi's financial position risked sliding out of control.
Less than a month before a national parliamentary election on Feb. 24-25, the case has also raised questions about lose links between Monte dei Paschi and local Tuscan politicians who dominate the shareholder foundation which controls the bank.
On Thursday, Bank of Italy deputy managing director Fabio Panetta defended the central bank's handling of the case, saying: "Our oversight has been continuous and impeccable."
European Bank Authority chief Andrea Enria defended the Italian central bank and said the case should not raise doubts about the solidity of the Italian banking system as a whole, pointing to other scandals, including Spain's Bankia, Franco-Belgian Dexia and Britain's Royal Bank of Scotland.
"As it was for Bankia, Dexia and the Royal Bank of Scotland, when you have a case of misbehaviour the responsibility lies principally with the management that did it," Enria, who worked at the Bank of Italy in the 1990s, told reporters in Milan.
However, the affair has raised speculation over the role of ECB President Draghi, who was governor of the Bank of Italy at the time of the Antonveneta deal and in the years when the derivatives trades were set up by Monte dei Paschi.
The Bank of Italy also drew criticism over former Monte dei Paschi chairman Giuseppe Mussari, who was re-appointed head of the Italian Banking Association (ABI) even though he had already left the Siena bank in a management clear-out.
Mussari was forced to step down from the ABI only last week, and its new head, Antonio Patuelli, said the central bank had made no effort to prevent last year's re-appointment. "There was no interference of any kind by anyone," Patuelli told Reuters.
His comment underscored questions over why the Bank of Italy did not take a tougher line against the troubled bank's former management, despite knowing about serious problems.
Mussari, who left Monte dei Paschi in April last year after it emerged the bank had booked big losses on derivatives contracts, resigned from the ABI when further derivatives losses emerged.
Prosecutors in Siena, the bank's home since it was founded in 1472, are investigating allegations that massive bribes were paid to smooth the Antonveneta deal as well as possible accounting malpractice over the derivatives trades.
They have revealed little about the substance of the investigation beyond saying it is focused on former managers as well as the bank itself as an institution.
On Thursday, they interviewed Ettore Gotti Tedeschi, head of the Italian branch of Banco Santander, the former owner of Antonveneta, and Gabriello Mancini, chairman of Monte dei Paschi's main shareholder foundation.
Monte dei Paschi's managing director Antonio Vigni also quit in last year's management clear out.