Finance Minister Grant Roberston says next week's Budget will contain $4 billion of savings and reprioritisations over the next four years.

Speaking to a business audience at Parliament, Robertson says ministers were told if they wanted to progress particular opportunities they had to look for savings opportunities within their ministries' existing budgets.

The $4b would mostly go towards funding agencies' existing cost pressures, he said.

The full details of what made up this number would be detailed when the Budget was released, but savings had been found across a wide range of areas, some of which had been well publicised already, he says.

They included closing contingencies the government wasn't convinced were still needed, reassessing forecast requirements of government departments and returning as savings underspends from existing initiatives.

Programmes such as the public media merger were stopped, the clean car upgrade and social leasing schemes curtailed, and funding associated with the affordable water reforms and Covid programmes that were no longer needed were returned.

Prime Minister Chris Hipkins has already indicated that costs the government will incur in the Cyclone Gabrielle recovery would be met within existing Budget funding and taking on some debt.

He has said the Budget will be "no frills" and also ruled out major tax changes like a capital gains or wealth tax.

The Budget will be yet another driven by a major economic shock. Robertson had been wrestling the books back into shape after the Covid-19 years, but now has to foot the bill for Cyclone Gabrielle and the Auckland floods, which will run into the billions.

-RNZ.