The Abbott government is refusing to release more detailed modelling prepared by Treasury in the lead-up to the budget that shows the likely impact of the planned budget measures on different household types.

Documents released under Freedom of Information to Fairfax Media show the federal government delivered its May budget fully aware its spending cuts would hit poorer households much harder than wealthier ones.

But two larger documents were withheld from the FOI request, a 56-page document and a 21-page document, and it is understood they starkly show how less-wealthy households suffer far bigger falls in disposable income than richer ones, especially for families with children aged between six and 16.

A spokeswoman for Treasurer Joe Hockey said the documents would not be released because they were prepared for cabinet and were therefore protected in the FOI process.