National's plan to expand the First Home Loan scheme could help more people buy their first home - but isn't expected to transform the housing market.

The party wants to widen access to five percent deposits.

If elected, National would increase the income threshold so anyone earning less than 300-thousand dollars combined could access the scheme - up from the current 95-thousand dollars for single buyers or 150-thousand for more than one.

Cotality Chief Property Economist Kelvin Davidson told Ryan Bridge the change will have a limited impact - and shouldn't push house prices higher.