It is claimed students and workers were using the service.
“They find, fake certificates as the way to get the visa in Australia,” said Ms Nguyen.
“If you pay money, your results will appear online, on the global IELTS website.”
Ms Nguyen spoke to one student who confirmed the rort.
“Don’t waste time on study,” the student told SBS. “Instead of spending money on education, save money and time by buying a fake certificate.”
“The fake IELTS result report is made so carefully and delicately,” she claimed. “Even a normal IELTS teacher could not tell the difference.”
The student claimed it wasn’t hard to find an unscrupulous provider: several websites advertise fake IELTS.
Migration agent Ha Nguyen said it could be lucrative.
“If you get an "eight", it’s like 20 points already, so it’s already a third of your application.”
But she warned a good score doesn’t always guarantee an applicant will get a visa, as there are other requirements too.
Institutions, such as Melbourne University, have strict online verification methods.
In a statement, the university said it "requires all agents to supply certified documentation, particularly with regards to academic transcripts, completion statements and English results".
Service provider to 140 countries, IDP Education, said in a statement, "Given the high-stakes nature of the IELTS test, there will always be a small minority of people who seek to attain results they haven’t earned".
Ms Ha Nguyen said there was still a way to verify someone’s English proficiency.
“You can ask for a test interview; you can actually tell whether their English ability is compatible with their score or not,” she said.
“We did have some cases in the past when we interact with students and they give us a certificate but we don’t think that it’s quite compatible with their English skill.”
Official IELTS teacher, Minh Nguyen, said many of her international students, including those from China and India, struggled with English.
She said she had heard of fake providers, but said it was not worth the risk.
“At the end of the day, if you decided to come in here and study, you have to use the language, you have to merge with the environment, and that’s what you can’t fake,” she said.
The Immigration Department said an applicant’s visa could be rejected or cancelled and it could impose a 10-year ban on future visa applications.