HSBC [NYSE:HBC] is preparing to appear before the U.S. Senate later on Tuesday to apologize after a committee report found that the bank had been used to launder billions of dollars in drug and terrorism money around the world.

The Senate probe, which also lays heavy criticism on HSBC's prime U.S. regulator, the Office of the Comptroller of the Currency (OCC), goes so far as to suggest that lawmakers should consider revoking the bank's charter to operate in the U.S.

In an age of international terrorism, drug violence in our streets ... and organized crime, stopping illicit money flows that support those atrocities is a national security imperative, Senator Carl Levin said, according to Agence-France Presse.

HSBC used its U.S. bank as a gateway into the U.S. financial system for some HSBC affiliates around the world to provide U.S. dollar services to clients while playing fast and loose with U.S. banking rules.

If an international bank won't police its own affiliates to stop illicit money, the regulatory agencies should consider whether to revoke the charter of the U.S. bank being used to aid and abet that illicit money, he warned.

The 335-page report from the U.S. Senate Permanent Subcommittee on Investigations, which draws from 1.4 million documents and interviews with 75 HSBC officials, describes a pervasively polluted culture and a dramatic failure of accountability at HSBC, according to Levin, the Committee's ranking lawmaker, Reuters reported.

His Committee accuses the bank of using a global network of branches and a U.S. affiliate to create a gateway into the American financial system that led to more than $30 billion in suspect transactions linked to drugs, terrorism and sanctioned companies based in Iran, North Korea and Burma.

Nearly $20 billion in HSBC transactions were found to have been linked to Iran or Iranian companies, the report said, with as many as 90 percent of them having no disclosure about their ties to the sanctioned Iranian government regime. Similar transactions were found linking HSBC to businesses in the Sudan, Burma and North Korea.

Investigators also allege that more than a $1 billion was shipped from the bank's U.S. units to an affiliate in Saudi Arabia, Al Rajhi, which has ties to terrorist groups. The report revealed that an HSBC attempt to cut ties with Al Rajhi in 2005, but the bank reversed the decision a few months later before exiting the business of shipping bulk cash altogether in 2010.

Further allegations include assisting the tax evasion of some U.S. citizens through HSBC India.