The impact on retailers from the Covid-19 lockdown is expected to be enormous

The latest data shows an overall zero point seven per cent decline in the March quarter - while supermarket sales leapt 8 point five per cent.

BNZ senior economist Doug Steel says it's a precursor to a much bigger fall in the second quarter of the year.

He says in April, electronic card transactions were down 50 percent and car registrations were down 90 percent, compared to last year.

Steel says if you factor in those numbers, there'll be a fairly chunky decline for the second quarter.

Doug Steel says panic-buying at supermarkets and liquor stores before lockdown skewed the figures for the first quarter.