Small business ombudsman Kate Carnell has called on the Morrison government to defer legislated increases to retirement contributions and cut super taxes, in a plan to help employers hit by COVID-19.

In a letter to Treasurer Josh Frydenberg, Ms Carnell said the government should take the pressure off small business operators through a two-year delay to increases in the super guarantee, set to take contributions to 12 per cent of wages in a staged increase from next July.