Assistant Treasurer Kelly O'Dwyer. Picture: Lukas Coch/AAP

Former Abbott government chief of staff Peta Credlin has criticised the planned $1.6 million cap on retirement-phase accounts as unfair because of retrospectivity provisions.

“It’s not retrospective — it’s a furphy. We changed the rate of taxation ... there’s nothing retrospective about that,” cabinet minister Steve Ciobo told ABC radio on Tuesday.

Tony Abbott’s former chief of staff Peta Credlin. Picture: Sam RuttynSource:Supplied

Assistant Treasurer Kelly O’Dwyer says the initial $1.6 million in super accounts can continue to grow tax-free.

“The capital itself will remain untaxed,” she wrote in an opinion piece in The Australian.

The change would affect just one per cent of Australians with a super fund account, and the government would consult on the changes to ensure there were no unintended consequences.