A letter addressed to the UK Financial Reporting Council (FRC) reveals that investors have expressed concerns regarding the lack of transparency surrounding how HSBC's auditor, PwC, verified the bank's accounting treatment. The letter was also copied to HSBC and the UK Prudential Regulation Authority (PRA). Signatories to the letter include Sarasin & Partners, workplace pension investor NEST, Merseyside Pension Fund, and asset management firms Lombard Odier Investment Management and Edentree Investment Management. (Reuters)