A stubborn Senate and falling iron ore prices have reportedly blown a $51 billion black hole in the budget.

An analysis by consultancy firm Macroeconomics shows the nation’s growth rate will slip to 2.1 per cent next financial year from the three per cent estimated in the budget, Fairfax Media says.

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Treasury had expected a $29.8 billion deficit this year to fall to $2.8 billion in fiscal 2018.

But the study found this year’s deficit would blow out to $47.8 billion and fall to $24 billion over three years.

The report attributes part of the decline to the iron ore price, which has fallen by $US20 a tonne since the budget’s release.

News of the budget hole comes as one of the Abbott government’s top advisers, Mark Textor criticised technology giants, like Apple and Google, for dodging tax on online content while TV channels paid.

He also accused business of not doing enough to sell GST reform.