Speaking on the BBC Today programme, former HSBC IT worker Herv Falciani said that the senior executives at the bank were aware that technology systems at its Geneva offices were in disarray, but failed to take action.
"The IT system had major issues," said Falciani. "For example, for eight months it was impossible to deploy new improvements of the system, and the system was victim to a lot of instabilities."
He added: "When you know that the IT system is the core of the bank, and without an efficient one it is impossible for the bank to complete its duty, it was impossible to have an efficient oversight of what was ongoing in the bank. And this was clearly documented and known at the highest level."
HSBC did not immediately respond to ComputerworldUK's request for comment.
Former systems engineer Falciani, from Monaco, joined the world's second largest bank in 2000, before transferring to HSBC Private Bank in Geneva six years later. Between 2006 and 2007 he collected confidential data on more than 100,000 customers from across 200 countries before sharing with the information with French authorities, and subsequently media outlets in France and the UK.
This week, the UK's Public Accounts Committee told the BBC that MP's were launching an "urgent enquiry" into the allegations.
Falciani has recently stated that the information publically available is the "only the tip of the iceberg", he told the Franco-Italian told France's Le Parisiennewspaper in an interview published on Tuesday.
"There's more than what the journalists have. Several million transactions [between banks] are also in the documents I transmitted. These figures could give an idea of what lies at the bottom of the iceberg."
The bank has come under criticism in the past for its lack of compliance controls. In 2012 the bank was fined almost £1.2 billion for failing to prevent money laundering by Mexican drug cartels, and was compelled by regulators on both sides of the Atlantic to improve monitoring systems. However, authorities have continued to attack the bank for failing to upgrade systems which lack "integration, coordination, and standardisation".
Other banks have come under scrutiny for lacking adequate IT controls. Last year, an investigation by the Financial Conduct Authority into another UK-based lender, Standard Bank, a subsidiary of South Africa's Standard Bank Group, revealed "serious weaknesses" in its AML procedures. This included failure to carry out adequate due diligence measures before dealing with customers connected to clients with a high risk of money laundering. The bank subsequently confirmed it has invested in upgrading monitoring systems, after being fined £7 million by the FCA.
According to a recent KPMG report, a third of senior banking executives believe that their anti-money laundering systems at their business are currently inadequate.
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