HSBC has a "terrible list of problems," its chairman admitted to an influential committee of UK lawmakers Wednesday.
Douglas Flint admitted to the UK parliamentary committee that oversees the financial industry that he couldn't rule out further scandals emerging at the bank along the same lines as the tax storm at HSBC's Swiss private bank, but said: "I sincerely hope there are no more skeletons."
MPs accused the bank of not being robust enough in its previous oversight of its Swiss banking operations.
The story surrounding erupted earlier this month when a cache of files taken by a former employee in HSBC's IT department, Herve Falciani, was reported on by several news organizations. Some of the clients whose details HSBC's Swiss operations were sheltering included arms dealers and politicians who were part of discredited regimes, like that of Bashir-al-Assad in Syria.
Earlier, when asked why some HSBC clients reportedly came to Switzerland with wads of cash, Flint was lost for words.
"It's completely unacceptable that some people pay their taxes and others don't," he said.
Stuart Gulliver, the bank's chief executive, said he and Flint had been "working tirelessly' for the past four and a half years to fix HSBC's problems, which they argued stemmed from a series of acquisitions in the 1990s.
Gulliver reiterated that in his personal tax affairs he had "followed the letter of the law."
Answering a barrage of questions from lawmakers, Gulliver said the practices at the Swiss Bank were "clearly unacceptable. We very much regret this,"
"I am responsible for clearing it up. I have made substantial changes," he said.
The hearing could contribute to HSBC's ongoing reputational crisis - and also potentially set the tone for tougher regulation on banks. With a general election in May – the result of which looks too close to call - MPs may be jockeying for position in the next Cabinet, and won't want to look like they're giving errant banks an easy ride.
Gulliver's own tax affairs have also been in the spotlight, after HSBC confirmed that he had a Swiss bank account, held via a Panamanian company, which he paid bonuses into in previous years.
The U.K.'s tax authority, Her Majesty's Revenue & Customs (HMRC), could still send more individual cases to its prosecutor for potential charges.
HMRC has had access to the files since 2010, but they have only resulted in one successful prosecution, together with around £135 million ($210 million) in fines and recovered taxes.
HMRC officials also face scrutiny by the committee on Wednesday.
HSBC's problems stretch beyond its Swiss subsidiary, however.
After disappointing results earlier this week, executives face questions over whether the banking behemoth, one of the two most systemically-important banks in the world along with JP Morgan, should be broken up to address weaknesses in its underlying performance. With such a huge global presence, it is perhaps inevitable that HSBC's performance will disappoint, as global economic figures come in weaker than expected.
However, there is increasing pressure to cut costs and possibly sell off underperforming regions like Mexico or Turkey.
- By CNBC's Catherine Boyle