None of the complainants - who alleged exam papers had been altered to ensure struggling TAFE students passed - were contacted as part of the investigation.

The Age revealed in March that four former teachers and two students wrote to the Independent Broad-based Anti-corruption Commission and claimed that in mid-2013 a number of Box Hill student's exams were altered, increasing their marks to the pass rate of 50.

They also contacted Training and Skills Minister Steve Herbert, who said the Education Department would investigate the claims.

One of the complainants, former Box Hill Institute teacher John Sier, said both parties should have been given the opportunity to put forward their evidence and views.

"If they are going to do an investigation, they have to speak to the people who are involved, it's called equality in law."

The whistleblowers also alleged that the TAFE failed to investigate concerns raised by three experienced teachers about suspected cheating by students.

Box Hill Institute chief executive Norman Gray, AM, said the allegations "were always going to be unsubstantiated".

"We welcomed this investigation in order to reassure the Victorian Government and the Victorian people, that we run a very ethical education business with fair outcomes for all students."

A spokeswoman for Mr Herbert said audit firm PPB Advisory had conducted a review to support the Department's investigation.

The whistleblowers were not contacted, she said, because there was "sufficient information available from detailed written information provided by the complainants".

One of the former teachers, who did not want to be named, said there had been no transparency.

"How can they possibly launch an investigation with just this? The Labor government has come to power promising to refund education and it would be very embarrassing for the government to find anything but exemplary conduct of Box Hill TAFE as it is the recipient of large amounts of government money."