Commonwealth Bank says it will not cut standard variable mortgage rates in response to the Reserve Bank's latest reduction in official interest rates, with chief executive Matt Comyn saying these are "unprecedented times".

Minutes after the Reserve Bank cut the cash rate to an all-time low of 0.25 per cent, CBA said via Twitter it would not cut standard variable rates on mortgages, but it would slash rates on small business loans by 1 percentage point.

"These are unprecedented times," chief executive Matt Comyn said. Credit:AAP

The bank also said it would cut various fixed-rate loans by as much as 0.7 percentage points, and increase one of its term deposit rates.

"These are unprecedented times, and they call for unprecedented measures," Mr Comyn said in tweet from the bank.