Annual net migration looks set to peak above 40,000, mainly due to more people choosing to stay in New Zealand, figures show.
New Zealand gained a seasonally adjusted 4080 migrants in April, compared with 3890 in March. April's figure is the highest since February 2003.
On an annual basis, there was a net gain of 34,366 migrants, compared with a net gain of 4776 in the April 2013 year.
Infometrics managing director Gareth Kiernan said the biggest contributor to the April lift was more people coming from Australia, with about two thirds of the lift in arrivals in the year being New Zealanders returning home.
"The pick-up in migration is being driven by the strength of the labour market within New Zealand and, comparing that to the labour markets overseas, particularly in Australia where their economy is struggling at the moment," Mr Kiernan said.
"So it's not a concern, I guess, that you've got people coming here to work because there are jobs for them but it does raise questions, particularly around the housing market and what sort of demand pressures and, potentially, price pressures are going to come through into the housing market through the rest of this year and into 2015."
Mr Kiernan said he believed there would be "significant demand pressures" on housing once the dampening effect of the Reserve Bank's low-deposit loan restrictions lifted.
"I don't think it's necessarily going to be as strong as we saw back in 2003-04, with the last migration boom, and that's partly a reflection of the mix of migration that we're getting at the moment, where it's not entirely being driven by more people coming here, it's also being driven by quite a big drop-off in the number of New Zealanders leaving.
"If it's fewer New Zealanders leaving, it also has implications in terms of the regional spread of people, and so it's not as concentrated in Auckland, whereas you can trust that with a big influx of migrants coming here, a lot of them in the first instance tend to settle in Auckland and place disproportionate demands on the housing market up there."
Mr Kiernan predicted double-digit house price inflation by the end of next year.