According to the Big Four firm's Focus on Transparency report, disclosures on the risks associated with liquidity, credit and the market are becoming more difficult to understand.
KPMG partner Bill Michael explained that the collapse of Lehman Brothers in 2008 created a "turbulent environment" that forced banks to begin releasing more information.
The average length of yearly reports increased by three per cent over the past year to 317 pages and Mr Michael added that there "are still wide variations in the level of details provided, the extent of risk disclosures, and the use of financial instrument categories".
Some key areas - such as accounting policies and financial statements - increased in length by 20 per cent, the report found.
A recent PricewaterhouseCoopers report suggested that asset management firms may need to alter their business models in order to survive the economic downturn.