The immigration department has rejected allegations of internal corruption, insisting there's no proof of staff criminality or fraud.
But the federal opposition has jumped on reports department officials have been referred to an agency corruption watchdog, accusing the government of undermining the visa system through neglect.
The department on Monday responded to an ABC/Fairfax report alleging more than 130 cases of suspected internal corruption have been referred to the Australian Commission for Law Enforcement Integrity.
The report cites a former immigration official claiming internal investigations found "massive fraud" in the student, skilled migration and 457 visa programs.
However, the department said there were no links to Australian Border Force or Customs staff as claimed, and most of those referrals related to people who claimed to be immigration officials.
Only a very small number involved actual staff.
"There is a very low threshold for the mandatory reporting of such allegations and many are yet to be assessed for veracity," it said in a statement on Monday.
"The allegations referred to ACLEI do not equate to actual instances of criminality, fraud or corruption."
Labor leader Bill Shorten demanded answers from the government after labelling the allegations as a major crisis.
If the reports were even half true, the government had undermined the visa system.
"This government has lost control of the visa system in favour of criminals and crooks," he told reporters in Melbourne.
Mr Shorten rejected suggestions the alleged fraud could have begun under Labor's watch in government.
Labor had instituted a Customs reform board that was sidelined in the coalition government's merger of Customs and Border Force, he said.
