The size of National's tax cuts seems to be growing, despite no further clarity for the public on what to expect.

Yesterday, John Key was saying Kiwi households might be $500 or $1000 better off each year from 2017.

Today, he told Palmerston North workers it might be $1500.

But he admits to media that all the figures are quite hypothetical, and he doesn't know how big any tax cuts might be.

"Well in the end anything is possible, we're not arguing that they're going to be massive tax cuts, we can't tell you exactly how much they will be per household, but they do matter."