Only a handful of immigration officials are working on processing investor visas that have a total value of more than $2 billion.
An immigration lawyer says the potential investment "locked up in an office in Wellington" needs to be freed up.
In a briefing to the incoming Immigration Minister, Kris Faafoi, immigration officials said business investor migrants had invested $1.36b in the first six months of this year.
But Immigration New Zealand (INZ) said it cannot legally grant new visas to people unlikely to get border clearance at the moment.
Figures show that since the end of April the number of investor applications "on hand" rose 44 per cent from 288 to 414.
But since July only 11 investor category 1 visa applications - with a minimum price tag of $10 million investment each - have been decided, and 17 in category 2, which has a minimum of $3m but tighter criteria.
Call for more resources
Immigration lawyer Simon Laurent said more resources needed to be focused on INZ's Migrant Investor Team to work on the lucrative visas.
"Just by doing a rough calculation based on the investor category 1 only, we're talking about $2b, on the basis that each of the investors when applicants would be seeking to invest $10 million.
"And even if we assume only half of the 400 or so applications in hand at the moment are approved, that is still probably about 200 applications at $10m each which are sitting in the queue.
"Certainly there's a great deal more interest from North America, the USA in particular, than there was a couple of years back. It used to be that Chinese applicants made up the bulk of the cohort.
"Furthermore - and this applies to those from the US in particular - they include an increasing number of capable entrepreneurs whose interest is in new ventures and new technology. The small, nimble New Zealand market has for some time been the test-bed for leading-edge developments.
"There may be real attraction in funding and supporting local businesses which are taking leading roles in areas such as biotech."
Laurent said the statistics indicated the processing of investor visas applications was very slow.
Verification of the source of funds could sometimes date back many decades and was too onerous, he added.
"I think we may be losing people because of this fixation upon ensuring that the money has been legally earned, especially by people who are reasonably high-profile and can demonstrate that they are in legitimate business operations. And that information for many of them would be available in the public domain."
He, and another lawyer spoken to by RNZ, have been told only two immigration officers are working on investor visas.
Border closures impacting process - INZ
In a statement, INZ said it has seven business immigration specialists assessing the visas alongside other applications such as global impact and retirement visas.
"While the borders are closed, INZ is legally unable to grant visas to individuals who are unlikely to meet entry requirements due to the current border restrictions," a spokesman said.
"This has had an impact on the processing of visa applications from individuals offshore, including the processing on investor category visa applications from individuals outside of New Zealand. However, INZ has continued to process visa applications from individuals who are already in New Zealand."
Chinese investor applicants fell from 71 to 41 in the past six months compared with the same period last year, while the number from the US grew from six to 38, continuing a trend that began with the Covid-19 lockdown.