Westpac is forecasting quarterly gross domestic product (GDP) growth of 0.7% to give an annual growth rate of 2.6%.
Reserve Bank governor Graeme Wheeler estimated last week economic growth was now 2% when he cut the official cash rate by 0.25% to 2.75%.
Mr Wheeler pointed to slower global economic growth due mainly to weaker activity in the developing countries.
He also warned the El Nino weather conditions could push New Zealand into a recession.
New Zealand Institute of Economic Research senior economist Christina Leung said yesterday the latest consensus forecasts showed a further downward revision in growth expectations among forecasters since the June survey.
''What stands out this round is the wider range of forecasts for growth, inflation and financial market measures, indicating a great degree of uncertainty over the New Zealand economic outlook.''
Activity indicators had softened over the past quarter, with the deterioration particularly apparent across confidence measures, she said.
Annual average economic growth was expected to track below 3% out to 2019.
Forecasters expected growth to ease to 2.5% in the March 2016 year before recovering slightly to 2.6% in each of the following two years.
Weaker household spending and business investment forecasts drove the downward revision to the growth outlook, Ms Leung said.
''The lower growth outlook is expected to flow through to a softer labour market with the unemployment rate now expected to hold up around the current 5.9% for the next two years.''
Westpac senior economist Michael Gordon said the forecast 0.7% increase in June quarter GDP followed a surprisingly weak 0.2% rise in March.
The previous weakness was partly due to three temporary factors over the quarter.
Milk production fell 3.6% as drought gripped much of the South Island, mining output fell sharply due to a partial shutdown at the Tui oil field, and low lake levels meant electricity generation shifted away from more efficient hydro generation during the December and March quarters.
''All of those factors were more than fully reversed in the June quarter. A strong end to the dairying season in the North Island meant milk production rose by an estimated 8% in seasonally adjusted terms.''
The Tui oil field returned to operation and recorded its highest quarterly output in four years.
Westpac had assumed a 5% rise in overall mining activity, given rising oil production might be countered by a further fall in exploration. And hydro's share of electricity generation had risen sharply, he said.
Removing those volatile items would suggest an underlying growth pace of about 4% for each of the last two quarters - not recessionary, but a meaningful slowdown compared with last year, when annual growth topped 3% for the first time since the global financial crisis.
Some of the detailed data Westpac had used to prepare its forecast gave cause for concern, Mr Gordon said.
The sharp fall in business investment seen in the March quarter did not appear to have been reversed and wholesale trade and manufacturing, apart from dairy, had fallen for two straight quarters. Those areas touched many parts of the economy.
''As we saw in the building work survey earlier this month, the construction sector remains an important contributor to growth at the national level. However, home building in Canterbury is now clearly past its peak. The growth is now being driven by commercial buildings and Auckland housing.''
Tomorrow, New Zealand's current account figures will be released by Statistics New Zealand. Westpac expected the annual deficit to widen from 3.6% of GDP to 3.8%.
That was not an alarming level in light of the history of New Zealand's current account deficit, Mr Gordon said.
Reporting the balance on an annual basis meant it tended to reflect market developments with a substantial lag.
The plunge in dairy prices to date meant the annual deficit was destined to keen widening further over the next year, peaking at 5.7% of GDP before receding.
