Australian immigration officials have been referred for investigation over more than 100 cases of alleged corrupt activity in Australia's skilled and student visa program.

Key points: Department investigations found "massive fraud" in Student, Skilled Migration and 457 visa programs, says ex official

Department investigations found "massive fraud" in Student, Skilled Migration and 457 visa programs, says ex official Up to 4,000 applicants lodged fake qualifications or counterfeit degrees to apply for skilled migration

Up to 4,000 applicants lodged fake qualifications or counterfeit degrees to apply for skilled migration Company caught rorting system given "slap on wrist" after sponsoring migrants for non-existent jobs

A 7.30-Fairfax Media investigation has discovered that in the last 12 months, Immigration Department chief Michael Pezzullo has referred 132 cases of suspected corruption inside the department to the national corruption watchdog, the Australian Commission for Law Enforcement Integrity (ACLEI).

It comes as a former immigration official claims that a focus on boat arrivals has allowed migration crime involving people arriving by plane to flourish unchecked.

"In the border security debate, it has been easy to deflect the public's attention to boat arrivals," said Joseph Petyanszki, who worked at the Department of Immigration for 27 years and was joint head of the Department's investigation office between 2007 and 2013.

"But this fear-mongering has totally ignored where the vast bulk of real fraud is, most significantly undermining our immigration programs."

He said the department was ignoring tens of thousands of cases of visa rorting, including thousands of successful visa applicants his investigators uncovered in Victoria, South Australia, Tasmania and Western Australia.

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Joseph Petyanszki has called for a major overhaul of the fight against migration crime. ( Supplied )

"Numerous investigations [by the department] revealed massive fraud within our Student, Skilled Migration, 457 programs," he said.

"Some investigations revealed thousands of skilled migrant applicants had lodged bogus qualifications from private colleges, funded by the Australian taxpayer, and in some cases excellent counterfeit degrees from our most prestigious Victorian universities.

"One investigation identified up to 4,000 applicants who used such documents to apply for skilled migration."

Mr Petyanszki is now calling for a major overhaul of the fight against migration crime.

"Australia needs many more officers who are trained to focus and understand fraud and assist decision-making officers in quarantining cases which may involve fraud," he said.

"There are also major integrity problems caused by outsourcing immigration work to migration agents who are largely poorly policed and regulated.

"Immigration laws are also beset with loopholes that can be exploited by unscrupulous migration agents.

"For years, the law, and the system, has favoured the arrive-by-place fraudsters at the expense of the integrity Australia's migration program."

A department spokesman said Border Force had spent 12 months ramping up its attack on visa and migration fraud.

"The Department's activities are focused on defeating visa fraud at the systemic level, including investigating and prosecuting networks involved in criminally exploiting Australia's visa regime," the spokesman said.

The spokesman also cautioned that many of the 132 corruption allegations had not been verified and some involved allegations about people who falsely claimed to be immigration officials.

Company caught rorting the system received a 'slap on the wrist'

Whistleblower Clint Raven was working for multinational construction contractor Murphy Pipe and Civil when he discovered his employer was sponsoring Irish nationals for jobs that did not exist.

Murphy Pipe & Civil was fined $3,500 and suspended from sponsoring overseas workers.

He has given sworn testimony to the Immigration Department about his former company, but has never spoken publicly about the company's practices, until now.

"As a business we were issuing or sponsoring visas for workers as project co-ordinators, project administrators, where that role didn't exist on our site and these people, their actual jobs was as a labourer on the ground," he said.

He believes what he discovered was blatant fraud.

"We would have employees be sponsored as quite a senior role but be operating an excavator or working as a labourer," he said.

"Many of these people didn't have the training even to operate machines when they came to the country."

Mr Raven said he had personally identified at least 30 workers at Murphy Pipe and Civil who appeared to be in breach of migration laws.

He suspects there were many more and said Federal Government-licensed migration agents were in on the scams.

Clint Raven discovered the company was sponsoring Irish nationals for jobs that did not exist.

"[People at the company] were working very closely with immigration agents that were requesting they change resumes to suit a role better," he said.

"[The migration agents] were advising them on loopholes."

Mr Raven took his concerns to the Immigration Department but said it did not appear to be serious about dealing with the visa rorting.

Murphy Pipe and Civil was fined $3,500 and banned from sponsoring any more overseas workers for four years.

According to Mr Raven, that was nothing more than a slap on the wrist for the company.

Australians 'missing out on jobs'

Murphy Pipe and Civil has denied rorting the visa system and is appealing the decision to ban it from sponsoring foreign workers.

"The issue is that Australians are missing out on jobs and there are people jumping the queue to gain residency into the country off the back of a mythical labour shortage," he said.

"These people are not only coming in as so-called skilled workers, they're in labouring positions that could be filled by a school leaver that's going straight on the dole queue."

He believes the extent of the rorting means it cannot have escaped the notice of immigration authorities.

"I think the sheer volume of it would've definitely raised some eyebrows about the 457 system," Mr Raven said.

"It was clearly, in this instance, just a means of getting people into the country to gain permanent residency."

Asked if he thought it was a form of people smuggling, he replied: "Exactly".