An ethics lecturer flashed his penis at a first-year student and threatened to fail another if she turned down his "predatory" advances.

Michael Montalto also tried to recruit 18 and 19-year-old students to have a threesome with him and his girlfriend, the Victorian Civil and Administrative Tribunal found on Tuesday.

The tribunal ruled Mr Montalto exploited the power imbalance with his students at a university in Melbourne, which can't be named, between June and August 2014 when he was 24 years old.

Mr Montalto denied the allegations, but the tribunal accepted the "consistent" and believable evidence from five women accusers, a male student in his ethics class, a course coordinator and another staff member.

Most of the allegations were made by a student who said she was bombarded with inappropriate texts and calls in 2014.