Treasurer Jim Chalmers has rejected criticism by Paul Keating and parliamentary crossbenchers over his proposal to hike taxes on high-value superannuation accounts, describing the changes as “modest” and indicating he won’t be open to amendments.

The proposal to double the tax on earnings on the portion of super accounts over $3 million has been slammed because the $3 million threshhold will not be indexed, and it will allow for the taxation of unrealised gains and the double taxation of judicial pensions.