(Reuters) -National Australia Bank ( NAUBF ) reported as much as 8% drop in its cash earnings for the third-quarter on Friday, hurt by rising competition in the housing loan market and higher operational expenses.

Banks are struggling to prop up their profits in recent times with stubbornly high expenses in general and intense competition in the mortgage market, as home loan borrowers look for better deals amid high repayments cost.

The bank said its asset quality deteriorated further in the third quarter, while net interest margin was stable with small reductions from lending competition and deposit mix, offset by benefits of a higher interest rate environment.

The country's top business lender posted cash earnings of A$1.75 billion ($1.16 billion) for the quarter ended June 30, compared with A$1.90 billion a year ago.

($1 = 1.5131 Australian dollars)