The Australian banking sector has hit back after an offshore analyst cast doubts on the arguments used by the local sector for justifying lifting mortgage rates independently of the Reserve Bank this month.

The Australian Bankers' Association chief Steven Munchenberg disputed the basis of the analysis that concluded the big four banks enjoyed an oligopoly in the local market, saying there was "no conspiracy" between major banks and lenders in Australia to unfairly lift mortgage costs for Australians.

"There is no conspiracy between the major banks, smaller banks, building societies and the RBA" ... Steven Munchenberg. Credit:Justin McManus

"There is no conspiracy between the major banks, smaller banks, building societies and the RBA, all of whom say the cost of funding has risen,’’ said Mr Munchenberg.

Mr Munchenberg's comments follow a scathing analysis from Tokyo-based Societe Generale Asia Pacific head of interest rate strategy Christian Carrillo, who yesterday said it was "almost mathematically impossible" that total funding costs for Australian banks were rising, giving the sector a motive to lift mortgage rates independently of a Reserve Bank this month.