The Geelong teacher who co-starred in an erotic video with a former student says he regrets the sex tape.

John Walsh resigned this week from his position as media studies teacher at Oberon High School amid a fierce backlash from parents and fellow teachers, after the online video was circulated on social media.

He told Ten Network's The Project that he understood the angry reaction caused by the tape.

"Hindsight is 20/20; I would not do it again, take the morality issue out of it, I think the hurt I caused, that really affected me. I'm very fond of the school," Mr Walsh said.