Australia’s four big banks recorded a near trebling in bad debts expenses to a 16-year high of A$6.5bn ($4.8bn), according to their latest half-year results, while provisions for problem loans more than doubled to A$16.3bn.

However, Australia’s big-four lenders – Westpac, Commonwealth Bank of Australia, National Australia Bank and ANZ – all remained firmly in profit and are among barely a dozen or so in global banking to retain AA ratings.