Labour Party leader Phil Goff has deflected questions about whether he knows the details of his party's fiscal plan, saying it is National's accounting that is shonky.
Mr Goff has come under fire for not being able to provide exact details in several media interviews on revenue projections for major policies such as the capital gains tax.
But Mr Goff says Labour has based its figures on data from the Treasury and has put out detailed costings.
He says he is not going to pretend to know every page of the Budget, but he knows the broad principles.
Mr Goff says John Key can't say how much National would get from its asset sales plan, and is pretending that doubling the number of superannuitants in the next 20 years is affordable.