Two of Australia's major banks have cut the interest rates paid to savers over summer, as average returns on a key type of savings account dipped below the rate of inflation.

In a sign of the miserable returns being paid to many savers, including retirees, analysis shows several banks, including ANZ Bank and Westpac, cut interest rates on savings accounts in December.

Canstar, an interest rate comparison website, said there had been 13 cuts in savings account interest rates across its database of banks in December, compared with only two increases. There were also 16 cuts in savings account rates in November, compared with one increase.

Westpac and ANZ were the largest banks to cut these rates last month, each lowering rates on online saver accounts by 0.2 percentage points, a sign lenders are competing less fiercely for this type of money.