KPMG is facing accusations of potential misconduct on both sides of the Atlantic after sacking one of its US partners and facing calls for an inquiry by one of the UK's biggest corporate governance advisers.

In a letter published in the Financial Times, Pensions & Investment Research Consultants (PIRC) said the recent Parliamentary Commission on Banking Standards report on the collapse of HBOS raised questions about the role of KPMG - its former auditor - and of John Griffith-Jones, chairman of the new Financial Conduct Authority (FCA). He had held the same role at the auditors when it signed off on the accounts of HBOS.

PIRC said Griffth-Jones helped set terms of the Financial Services Authority's inquiry into HBOS's collapse - terms that excluded the role of auditors.

"It cannot be right that the chairman of the new FCA has any link with the second largest UK banking collapse in history," the letter, written by PIRC managing director Alan MacDougall read. "He should at least step down until the performance of KPMG in the audit of HBOS, and accounting standard setting, has been properly and independently investigated."

The FCA - Britain's newly-formed financial market watchdog - is due to publish a report into the failures at HBOS later this year. It does not have the power to regulate or punish auditing firms but it can comment on audit practices as part of its own investigation into the collapsed bank.

The Financial Reporting Commission, which oversees auditing firms, told Reuters it had not yet decided whether to conduct an investigation into KPMG.

"We don't currently have it under investigation but we are monitoring the situation quite closely with everything that is going on at the moment, and then we will take a decision whether or not to start an investigation."

Late Tuesday it emerged that KPMG had fired a Los Angeles-based partner, Scott London, after he was said to have leaked sensitive information about one it clients - sports shoe maker Skechers USA - to a stock trader for profit.

"I regret my actions in leaking non-public data," said London in a statement published in the Wall Street Journal. "KPMG had nothing to do with what I did. The firm bears no responsibility in this matter. These actions were by my choice and mine only."

Skechers and another US-based company, Herbalife, have both said they are withdrawing KPMG as their auditor. Herbalife said in a statment that an internal KPMG investigation found that a partner in the firm had allegedly been trading shares in the nutritional supplement company.

Bloomberg news has reported that both the US Department of Justice and the Securities and Exchange Commission are investigating.