Inflation is expected to have risen sharply in the three months ended December because of higher petrol prices and a rise in GST to 15% on October 1.
Statistics New Zealand will publish the latest consumer price index (CPI) figures on Thursday. The CPI is the official measure of inflation.
Westpac and the Reserve Bank expect inflation to have risen 2.3% in the quarter to give an annual inflation rate of 4%. ASB is forecasting a quarterly increase of 2.6% and a 4.3% annual rate.
ASB economist Christine Leung said that, given there had been mixed anecdotes about whether businesses had passed on the GST increase fully, there was greater-than-usual uncertainty over the forecast.
How households and businesses responded to the inflation spike would influence monetary policy.
"We expect the Reserve Bank will become less comfortable with the inflation picture later this year."
Combined with other Government policy changes - including higher energy costs related to the emissions trading scheme, the tobacco excise tax increase and higher ACC levies - Ms Leung expected the annual rate of headline inflation to peak at 5.3% by June.
There seemed little urgency for the Reserve Bank to increase the official cash rate and the ASB now expected the OCR to be lifted in September, rather than June.
Westpac markets economist Michael Gordon said that while higher fuel prices would be boosting inflation this year, the Reserve Bank would largely ignore it.
"Higher petrol prices are a drain on consumers' purchasing power of other goods and this weakened demand lowers inflation pressure elsewhere in the economy."
Fruit and vegetable prices fell in November but high commodity prices were likely to flow through into higher food inflation in coming quarters, he said.
Housing rents had also risen and Mr Gordon expected the Canterbury earthquake to have further boosted rents.
Westpac was also picking September for the next OCR rise.
