Four academics at a Melbourne university have been stood down after they allegedly "gouged" students, forcing them to buy unauthorised e-books in order to pass subjects.

RMIT University says the School of Economics, Finance and Marketing academics have been stood down pending an investigation.

AAP understands the academics are lecturers and that students in some business subjects had to complete mandatory online assessments via the e-book company website in order to pass.

Introductory finance course, business finance, is one of the subjects that require an e-book to pass, RMIT student Adam Yehia told AAP.

"This course in particular has a reputation amongst students for gouging them by forcing (them) to purchase the e-book, regardless (of) if they can afford it," he said.

"There is simply no other option of completing the mandatory four online assignments... which amount to a total of 50 per cent of the final grade."

A Semester 1 2017 course guide for the subject confirms the four online quizzes are compulsory and only accessible by purchasing the e-book, which cost about $50 a book.

The books cannot be resold, transferred to another student or shared.

The National Union of Students has slammed the academics.

"Forcing students to pay for any reading that isn't authorised under the curriculum is a breach of the trust between student and teacher," National Union of Students President Sophie Johnston told AAP.

She said the e-books were a serious financial barrier for students wanting to undertake university studies.

"Students fork out hundreds of dollars every single semester and intentionally adding to this burden is unacceptable," Ms Johnson said.

RMIT University would not confirm if the e-book tests were a compulsory part of students' curriculum, but said they were against policy.

"The alleged unauthorised sale of e-books in order to do online quizzes appears to go against university policy," Professor Ian Palmer, Pro Vice-Chancellor of Business and Vice-President, RMIT University said in a statement.

"While academics are encouraged to publish and promote their work, materials and assessments must comply with university governance arrangements."

Auditors Pricewaterhouse Coopers are investigating the academics' conduct with all four staff stood aside on full pay pending an outcome.

The university says students taught by the academics will not be affected and classes will run as usual.