Nathan Zamprogno taught across Sydney's private Christian schools for 20 years, but he says once a school discovered his sexuality, he was sacked.
"When I was challenged about my sexuality, I answered honestly and I was told there was no place for me at the school the following year - the connection was crystal clear," he said.
"I was well regarded in that community among my students and my peers, and I was good at what I did and never dishonoured my employer. My sexuality had nothing to do with my ability to do my job."
Mr Zamprogno, who is now a Hawkesbury City councillor and a Liberal party member, heard discriminatory remarks from the very top of his organisation.
"The headmaster would casually say in a staff meeting 'oh, I wouldn't employ a gay teacher'. I would shrink into the corner and a part of me would die inside," he said.
At a Senate inquiry into the religious discrimination bill, Mr Zamprogno said any evidence schools did not use their power to discriminate against employees on the basis of sexuality was "simply untrue".
He called on the government to abandon the bill or fix "the egregious loopholes that allow discrimination against people like myself".
"The provisions of this bill effectively empower those who want to put pressure on and ultimately purge people of a different religious conviction to themselves," Mr Zamprogno said.
"Worse, this bill would side with those who are less moderate, less compassionate. I don't think the parliament should be weighing in and taking sides."
Another teacher, Karen Pack, a lesbian and Christian woman, told the inquiry she was let go by a Sydney college when she became engaged to her wife.
After the school began receiving hostile phone calls and emails, she was told she could no longer work there.
"A letter was sent saying the principal with the support of the board had determined I could no longer work at the college ... that document also praised the depth of my Christian faith and my excellence as a teacher," she said.
"It was very clear the problem wasn't my theology, my teaching or my character - it was purely because I was gay and getting married to my partner."
Ms Pack said the legislation "was an attempt to purge the church of people like myself".
The religious discrimination bill is designed to protect those expressing religious beliefs as long as it isn't done maliciously or in ways that vilify, threaten or intimidate others.
The inquiry continues.
Australian Associated Press
Sign up for our newsletter to stay up to date.