The Herald on Sunday captured a picture of protestors with handwritten signs saying "lesbi/gay copy ... animals" and any MPs who supported the bill to legalise same-sex marriage were "mantally sick".
Anti-equality Labour MP Su'a William Sio was in attendance, as was National's Kanwaljit Singh Bakshi, who is a member of the Parliamentary committee that will consider public submissions for and against the Marriage Amendment Bill.
"I tell you, the majority of the National Party MPs voted against this bill,â€ť Bakshi incorrectly told the crowd, later conceding to the Herald on Sunday that was untrue.
Alani Taione from the Tonga Development Society referred to the Prime Minister as "John Gay".
Attendance estimates at the protest, arranged by 30 churches, range from just 250 to 300 people.
Gay MP Kevin Hague has responded by tweeting the rally â€śshows opposition to the Bill is based on fear and ignorance, not rationalityâ€ť.
He has also quipped, â€śHmm. So I'm confused: am I copying animals or unnatural?â€ť
Hague will be on the select committee and says he is â€ślooking forward to more sparkling debate like this with Mr Bakshiâ€ť.
There was also a small gathering of 80 protestors on Parliament's steps on Saturday.