Impaired assets at National Australia Bank increased by a quarter over the June 2009 quarter, while the level of the better-secured delinquent loans increased only marginally over the same period.The "risk and capital report" for NAB for the quarter, and published yesterday, shows impaired loans jumped to $5.4 billion at June 2009 from $3.9 billion at March 2009. Past due loans increased to $2.3 billion from $2.1 billion. This is the new quarterly report also known as the "pillar 3" report.The bank reported essentially no growth in credit exposures over the June 2009 quarter, with "exposures at default", to use the jargon required by APRA's reporting standards, declining by $2 billion to $652 billion.NAB published some of this data, albeit in a compressed form, a month ago in its trading update for the June 2009 quarter.NAB said then that cash earnings for the June 2009 quarter were around $900 million. This compares with cash earnings for the March 2009 half year of $2.02 billion and average cash earnings over each of the six quarters to March 2009 of $990 million.The bank also said increases in troubled loans were most problematic in the bank's institutional banking business and also in Britain, with the level of loan strife rising more modestly in Australian business and retail banking.