The federal government is refusing to release more detailed modelling prepared before the budget by Treasury, that shows the likely impact of the proposed measures on different household types.

Documents released under freedom-of-information legislation to Fairfax Media show the government delivered its budget fully aware its spending cuts would hit poorer households much harder than wealthier ones.

May budget: Impact on low-income households was known. Credit:James Alcock

But two larger documents were withheld from the FOI request, one of 56 pages and the other of 21 pages. It is understood they show clearly how the less wealthy households would suffer far bigger falls in disposable income than richer ones, especially for families with children aged between six and 16.