Prime Minister John Key says the changes to KiwiSaver which the Government will announce in next week's budget will not represent a broken election promise.
In 2008, National campaigned on reducing the minimum contribution level and removing the employer tax credit, both of which have been implemented.
Further to that, the party promised that KiwiSaver members would keep their current entitlements under a National Government.
Mr Key says he acknowledges the scheme is valued by New Zealanders but changes will have to made to keep it sustainable.
Labour says this represents another broken promise, following the increase made to the Goods and Services Tax (GST).
The Green Party says National will be on shaky ground if it makes any further changes to what it campaigned on.
In a speech on Wednesday, Mr Key will indicate what changes the Government wants to make to the savings scheme.
He will also touch on interest free student loans, and working for families, but the details won't be released until Budget Day on 19 May.