As Treasurer Joe Hockey drafts Australia's most brutal budget since 1996, he is warning "every sector of the community" to brace for cuts. But there remains one enormous exception.

While Mr Hockey named defence last week as one of the four biggest and fastest-growing areas of Commonwealth expenditure – welfare, health and education are the others – there will be no meddling with the $25 billion defence program.

Liberal MP Stuart Robert. Credit:Alex Ellinghausen

"Whilst Joe’s right that everyone has to share the pain ... with respect to the budget cuts it’s everyone but defence," Assistant Defence Minister Stuart Robert says.

And to squash any doubt, Mr Robert leans across the desk of his Parliament House office.