The Government has shut down its visa processing operations in Iran after it was warned some migration agents were boasting of corruptly obtaining visas through a contact in the Australian embassy in Tehran.

The ABC understands the allegations, outlined in a letter sent to the embassy in January 2017, were then referred to Australia's peak corruption watchdog, the Australian Commission for Law Enforcement Integrity (ACLEI), for investigation.

The visa processing section at the embassy was shut down in July last year.

The ABC has been told that investigators — believed to be from ACLEI's Visa Integrity Task Force — have questioned several Iranians in Australia about the circumstances in which they obtained their visas.

The case raises further concerns about the integrity of Australia's visa system.

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The ABC has previously reported on a fake 457 visa scam and unregistered agents ripping off their clients to the tune of tens of thousands of dollars.

In the letter, a group of Australian-based migration agents who deal predominantly with Iranian clients warned certain migration agents in Australia were boasting of having a special relationship with a contact in Tehran and were charging Iranians in both Iran and Australia tens of thousands of dollars in exchange for visas that normally cost a fraction of that.

The letter from the Australia Iran Migration Consultants Association drew attention to an increase in the number of Iranians who were receiving temporary entry visas, despite having relatives in Australia on protection visas. There is ordinarily little chance of having such visas granted, due to the likelihood the family members will arrive here and also apply for protection.

"These applications were not based on compelling and compassionate reasons and were not endorsed by an Australian government organisation," the letter said.

"We request the embassy investigate the allegations and let our Association members be assured that the decision of refusal or granting the visa to the applicants is based on the Australian Migration Act and Migration regulations."

The head of the association, Mohammad Reza Azimi, told the ABC a senior official from the embassy responded, asking for specific information to back up the allegations.

Head of the Australia Iran Migration Consultants Association, Mohammad Reza Azimi. ( ABC News )

"They asked us for the names of those people who we believed are involved in some sort of corruption. We had several meetings within the Association, because that's a very sensitive thing, and we asked if the confidentiality of the Association would be maintained if there was any sort of FOI request," Mr Azimi said.

"We were not reassured they could maintain the confidentiality of the Association, so we said we can't provide the names.

"We asked the department to do an investigation. They can just draw the information from the system, for example, on how many visitor visa applications [each agent] lodged in the last five years, compare it to the others, look into the merits of each case and you will find the answer. The Embassy didn't get back to us. We don't know what the outcome was."

Since the closure of the visa processing section at the Tehran embassy last year, visa applications by Iranians have been diverted to other Australian embassies in the region.

The Department of Home Affairs declined to answer directly whether concerns about possible corruption lay behind the decision

Instead, the department said in a statement the decision to close the office in Tehran "aligns with Home Affairs' continuing expansion of its online services."

Concerns around Home Affairs employee

The ABC has been told of a number of concerning relationships between one person employed in the Tehran visa processing section and some migration agents in Australian and Iran.

Visa processing is now conducted online or in countries outside Iran. ( AP: Ebrahim Noroozi )

One migration agent recently had her registration cancelled by the industry's regulatory body because she charged large fees but failed to secure visas for her clients.

She also improperly levied $50,000 bonds on temporary visas applications, which were to be repaid when clients returned to Iran from Australia.

According to the published decision to cancel her registration, when questioned by officials from the Office of the Migration Agents Registration Authority about the bonds, she said: "She used to collaborate with a colleague in Tehran to follow-up on these visa matters as he was well-known within the Australian embassy, where visitor visa applications were processed, for lodging visitor visa applications for genuine visitors [and] he advised that we should obtain some bond money to ensure [the client] complied with his visa conditions."

There is no suggestion within the decision that the agent has made payments to improperly obtain visas.

The colleague she referred to has been identified to the ABC by a number of sources as an Iranian businessman who has allegedly been able to obtain visas from the Tehran embassy that would not ordinarily be granted.

It has been alleged the man has particularly close ties to a Department of Home Affairs employee in the embassy.

The ABC has confirmed the embassy employee has approved visa applications for the Tehran-based businessman, dating back at least nine years.

In Australia, it is necessary for somebody to be a registered migration agent before they act for clients seeking visas, whereas there are no such restrictions in some countries overseas.

The ABC has also been given the names of two Iranian businessmen who obtained visas — one for himself; the other for family members — in circumstances where visas would not ordinarily be issued, allegedly by using the services of the Tehran-based businessman.

The ABC asked the department about relationships between the embassy employee and migration agents, and a spokesperson replied: "As an agency subject to the Law Enforcement Integrity Commission (LEIC) Act 2006, the Department of Home Affairs must notify all corruption issues to the Australian Commission for Law Enforcement Integrity."

The Visa Integrity Task Force was set up in 2017 to investigate allegations of visa fraud involving Department of Home Affairs staff, and comprises staff from the department, ACLEI and the Australian Federal Police.

While the timing suggests the January 2017 agents' letter may have prompted the creation of the taskforce, it is not know what specific concerns led to the decision to establish a dedicated unit to investigate possible visa corruption.

Last year, two staff members at the Australian High Commission in South Africa were sacked after an ACLEI investigation found they had issued visas to high-risk Nigerian students in exchange for cash.