A group of up to a dozen Coalition MPs are now in open rebellion against the government's planned increases to compulsory superannuation, warning Treasurer Josh Frydenberg they are "frustrated" by his position to raise the rate from 9.5 to 12 per cent.

Finance Minister Mathias Cormann moved to swiftly shut down the uprising, which has grown from two MPs to a dozen within a matter of weeks, as concerns grow that it would be unethical to put more workers money into an inefficient system worth almost $3 trillion.

Finance Minister Mathias Cormann and Treasurer Josh Frydenberg are facing an uprising of Coalition MPs over superannuation increases. Credit:Alex Ellinghausen

Senator Cormann ruled out changes to the legislated timetable on Tuesday that will see super increase gradually to 12 per cent from 2021 in a move the Grattan Institute estimates will cost workers up to $20 billion a year in wages once it is fully implemented.

The Morrison government is preparing to announce a retirement income review that will take into account superannuation, pensions and taxation following a recommendation from the Productivity Commission, of which the scheduled rise to 12 per cent is expected to form a key part.