Big banks say just one in 10 borrowers lowered their home loan repayments when the Reserve Bank of Australia cut interest rates in May, reducing their mortgages faster instead of spending the savings.

Traders have all but priced in a certain cut on Tuesday, making it the third for the year and reducing interest rates to 3.6 per cent, their lowest in two years. But the data from Commonwealth Bank, National Australia Bank and ANZ suggests the cuts are not necessarily leading to higher spending.