The central bank sought to slow demand in the property market in recent years through loan-to-value ratio restrictions, first implemented in 2013. More recently, the Government banned the sale of residential property to foreign buyers under new rules that came into effect this month.
But S&P Global Ratings still believes the risk of a sharp correction in property prices remains elevated because of the historical build-up.
If a sharp correction were to occur, the New Zealand economy's external weaknesses, in particular its persistent current account deficits, would amplify the impact on financial institutions, it said.
It said there is potential for an easing of the economic risks the banking system faces if the four-year average growth of inflation-adjusted house prices remains below 8 per cent, and the four-year average growth of private sector debt to GDP remains below 2 per cent.
It also said the trend for industry risks in New Zealand's banking sector is stable.