The additional spending doesn't threaten fiscal stability with government debt still declining as a share of GDP, it said. The OECD forecast government gross debt would fall to 35.6 per cent of GDP in 2019, from 35.7 per cent in 2018 and 36 per cent in 2017.
It expects the Reserve Bank to withdraw some monetary policy stimulus in 2019 through higher interest rates in order to slow inflation stoked by capacity constraints and increasing import prices from New Zealand's main trading partners. The consumers price index is seen running at 2.1 per cent in 2019, from 1.7 per cent in 2018.
"A sharp housing correction is the biggest downside risk, as household debt has risen to high levels relative to income, and most mortgagees have interest rates that are floating or will be repriced within two years," the report said.
"Conversely, short-term growth could be higher if housing shortages in Auckland trigger further price rises and associated wealth effects."
The OECD said projected increases in interest rates and government spending will improve New Zealand's macroeconomic policy balance and both should also serve to reduce housing market pressures.
Still, it said the resolution of infrastructure and planning constraints in Auckland is critical to easing affordability challenges, boosting weak productivity and avoiding a further house price breakout.