Labour finance spokesman Grant Robertson says Prime Minister John Key is refusing to give up on his dream of tax cuts for the wealthy, despite being shot down by the Finance Minister, and is picking numbers out of thin air.

The Prime Minister has outlined the three options his Government has on the table when it comes to offering tax cuts.

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They're off the agenda when it comes to next week's Budget, but John Key isn't ruling them out as an option next year.

He said they could be offered in next year's Budget or the Government could signal next year it intends to campaign on offering tax cuts.

"I suppose the third option is always that you say, we're taking that off the table, but if you take the latter, that's certainly not where our thinking is at the moment. We'd like to deliver a tax cut to the electorate the question is the timing of that and the size of it."

The Soap Box: Key's possible tax cut is hip-pocket politics

However there are questions about what the true cost of tax cuts would be.

Grant Robertson said Treasury is predicting a $1 billion surplus for next year, which means another two billion would need to be found somewhere.

"Even at their most optimistic the Government going to need to find an extra $2 billion and that can only come from cutting services or potentially selling off more assets."

Robertson argues that by discussing tax cuts, the Government's priorities are all wrong.

He said when people are being forced to live in cars and garages, when older New Zealanders are living in pain because they can't get operations, "we're a long way from being able to afford these kinds of election bribes."