Indian student visa fraud is snowballing, despite Immigration New Zealand's clampdown, and the Labour Party says fraudulent applications in the sector are now endemic.
Immigration New Zealand (INZ) began a crackdown on forged bank documents from Indian students in May.
It has been warning private training schools and polytechs every time an Indian education agent submits a fraudulent application.
However, new figures released to the Labour Party under the Official Information Act show the total number of cases of fraud had grown from 75 cases involving 60 agents in April, to 640 cases and almost 300 agents by mid-August, since INZ's clampdown began.
The INZ documents said agents were inventing new types of fraud, now that fake bank documents were being curtailed, such as using "rent-an-uncle loans" in which students pretended their finances came from family members.
The fraud detection rate at the Mumbai INZ office has dropped to a dozen cases a week, down from about 40 in April.
But 30 new Indian education agents were popping up every month - though their applications were immediately put in a 'not trusted' basket.
Four out of five of these new agents' visa applications were being rejected.
A quarter of those agents were not actually new, but were companies that had rebranded themselves to try to get a clean sheet.
An 'arms race' between agents and INZ - Labour
Labour's immigration spokesperson Iain Lees-Galloway said the fraud was endemic and putting a big strain on INZ.
"These immigration agents are changing their tactics constantly so that there's something of an arms race occurring, where Immigration New Zealand detects a certain type of fraud, they crack down on that and the agents are engaging in a different type of fraud to try and get through," he said.
He called on INZ to apply more pressure in New Zealand by releasing the names of the schools in this country subject to high rates of fraudulent visa applications.
Those names were redacted from the OIA documents, which showed 395 student fraud cases at the worst-hit 15 education providers.
There were 47 fraud cases detected at a single provider this year.
"There are some providers that have a large number of rejections... If we knew the names of the providers I think it would change the behaviour of those providers very quickly," Mr Lees-Galloway said.
He would be challenging INZ's redaction of the names with the Ombudsman.
He also called on INZ to publish the visa rejection rate for the various schools online, in the same way that it does for the rejection rate of Indian agents.
The clampdown at the agent end was complicated by the fraudsters' changing tactics, Mr Lees-Galloway said.
"The alternative approach is to put the responsibility on the providers so that they have to go through a much more rigorous process when they are engaging these agents and make sure they are only engaging agents who are acting lawfully."
Edwin Paul, who advises polytechnics on international recruitment, said tertiary institutions were weeding out bad education agents - but that would not stop people from making fraudulent applications.
"The number of applications will still be there on the ground because it's a country of a billion people and a few thousand agents.
"The ones who are new will still try, but I think from our side the clampdown is working pretty effectively."
Mr Paul said the fact fraud was being detected indicated Immigration New Zealand was doing its job.
INZ appears limited in what it can do. The documents showed it needed a school to get a signed waiver from an agent before it could share that agents' performance details with the school.
RNZ approached INZ for comment night but they did not respond.
Dozens of Indian students face deportation from New Zealand over forged documents, though in many cases they argue it happened without them knowing.
There are also reports of students engaging in crime, prostitution and being exploited at jobs with illegally low pay, who may have been allowed in because it appeared their finances were healthy when they were not.