“If you’re worried about religious freedom and freedom of speech, vote no, and if you don’t like political correctness, vote no because voting no will help to stop political correctness in its tracks.”

Those were the words former prime minister Tony Abbott used to kick off his campaign of opposition to same-sex marriage after the announcement of the postal survey.

Abbott was one of the most high-profile campaigners against marriage equality but a poll obtained by Guardian Australia suggests far from helping the no campaign, his unpopularity was lead in its saddle bags.

Confidential campaign-tracking polling conducted by Newgate Research for the Equality Campaign found that on 12 September, Abbott had a net favourability rating of -28% when respondents were asked to rate his contribution to the marriage debate.

The poll was taken after a month of campaigning and a bruising public debate between Abbott and his sister, Liberal Sydney City councillor Christine Forster, who publicly rejected his calls for people to vote no as “simplistic and inaccurate”.

The campaign went from bad to worse for Abbott, when he claimed an assault against him in September was a politically-motivated act of violence from a yes campaigner. The man behind the assault later said it had nothing to do with marriage equality.

Abbott’s daughter, Frances, then appeared in an ad for the Equality Campaign backing same-sex marriage, saying “you can’t help who you fall in love with”.

Abbott stayed on the attack, claiming that US rapper Macklemore had inappropriately politicised the NRL grand final by playing his hit song Same Love.

After that incident in early October, Abbott was less vocal in the no campaign, leading to speculation among marriage equality supporters that he had been benched.

In November, Abbott re-emerged, giving a speech to the anti-gay Alliance Defending Freedom group, which is classed as a hate group by the Southern Poverty Law Centre, saying a 40% no vote in the postal survey would be a “moral victory”.

The no campaign failed even this modest target – with 38.4% of the vote in the survey. In Abbott’s electorate of Warringah, 75% of those who responded voted for same-sex marriage.

Abbott – who devised the Coalition’s policy to hold a plebiscite while he was prime minister in 2015 – then took credit for the outcome.

“I put this process in place. I have, in a sense, facilitated the change,” he told 2GB Radio. “I certainly intend to facilitate the passage of a bill.”

He then lobbied for a conservative same-sex marriage bill, which was withdrawn – and amendments, which all failed.

In debate on Thursday before the cross-party bill passed the House of Representatives, Abbott called for the views of the 5 million Australians who voted no to be respected.

He targeted Malcolm Turnbull and Bill Shorten for having pledged to protect religious freedom and freedom of conscience, complaining that the “promise made by the leaders of this parliament ... has not adequately been delivered upon”.

When the vote was called, just four MPs opposed the bill but Abbott was absent from the chamber, indicating that he abstained.

A spokeswoman for the Coalition for Marriage paid tribute to Abbott, saying he was “integral in securing the millions and millions of no votes that occurred during the campaign”.

“He is the only prime minister or opposition leader in recent memory, other than John Howard, to have not flipped and flopped on the issue of traditional marriage and freedom of conscience,” she said.

“It is this sort of consistency and message cut-through that makes Tony Abbott such a successful campaigner and leader.”

Guardian Australia has contacted Abbott for comment.