The Samoa Observer newspaper reported Tuila'epa Sa'ilele Malielegaoi saying the Opposition argument reflected ignorance.
During the last session of Parliament this week, Tuila'epa ordered the inquiry into four Opposition MPs, including his former deputy, Fiame Naomi Mata'afa for alleged treasonous activities and breaches of Standing Orders.
Tuila'epa said the MPs had been campaigning when they should have been in parliament.
But Fiame said she was not concerned by something that was "quite ridiculous".