Housing affordability is at its worst in more than two decades, with both aspiring homeowners and low-income tenants slammed by surging prices, rents and interest rates, the latest ANZ Housing Affordability report shows.

The average portion of income needed to service a new mortgage blew out to 48.9 per cent nationwide during the March quarter, up from 43.1 per cent a year ago and a sharp jump from the 34.8 per cent decade average.