Malcolm Turnbull has warned Tony Abbott against a procedural move that could delay marriage equality and force parliament to return next week after more than 30 hours of debate in the lower house.

The stoush in the Coalition party room on Tuesday came as marriage equality advocates were increasingly confident the cross-party group has the 74 votes required to block any substantive amendments to the Senate marriage equality bill.

Abbott and fellow Liberal backbench MP Kevin Andrews told the Coalition party room they intended to move a “pious amendment” which would not block the cross-party same-sex marriage bill, but would reaffirm the importance of religious freedom.

Such a manoeuvre would reset the lower house debate back to the start of the second reading stage, which has already run all Monday and will continue with extended sittings until midnight Tuesday and again on Wednesday.

According to a Coalition source, Turnbull said he takes traditional marriage “very seriously” but warned the Abbott amendment must not be allowed to derail the bill before consideration of substantive amendments in the committee stage.

The leader of the house, Christopher Pyne, said if the Abbott amendment were passed it would “negate” the bill. Several others, including Trent Zimmerman, spoke against Abbott’s plan.

The overwhelming sense in the Coalition party room was not to delay the same-sex marriage bill, with negligible support for Abbott’s procedural move.

However, if Abbott goes ahead with the plan, it will give opponents of same-sex marriage and advocates of religious freedom a chance to show their numbers before the final vote, in which many have pledged to vote for same-sex marriage because the postal survey showed that 61.6% of Australians wanted them to.

Conservatives have indicated they will also re-propose substantive amendments that were put to the Senate but rejected.

Turnbull has said he supports at least two amendments to guarantee that charities will not be affected and to allow civil celebrants to refuse to solemnise same-sex weddings.

A bloc of 73 members from Labor, the Greens, Rebekha Sharkie, Andrew Wilkie and Liberal MP Warren Entsch have said they will oppose all amendments.

Although no final 74th MP has publicly committed to oppose all amendments, marriage equality advocates are confident the bloc of the bill’s co-sponsors Tim Wilson, Trevor Evans and Trent Zimmerman will provide crucial votes when amendments are considered.

The independent MP Cathy McGowan is also reported to be unlikely to support amendments but has reserved her final position until the debate concludes.

Asked on Tuesday about the fact government members may not back the amendments, Turnbull said Coalition MPs had a “free vote” and had the “absolute right” to vote on amendments as they wish.

On Monday evening the immigration minister, Peter Dutton, all but conceded the amendments did not have the numbers. Dutton said it was “very hard to see” how proposed “protections” for religious freedom would pass the house, expressing hope amendments would succeed but adding “the arithmetic in my opinion dictates otherwise”.

Zimmerman told the house the cross-party bill “will deliver the marriage equality the Australian public voted for”.

“Not one word or one clause will change existing rights of religious freedoms,” he said.

On Tuesday the Australian Marriage Equality co-chair Alex Greenwich said that advocates took nothing for granted but urged parliament to pass the cross-party bill unamended to “stop playing politics” with LGBTI people’s lives.

Fellow co-chair Anna Brown accused conservatives of putting up “further elements to distract, to delay, to attempt via amendments to turn the no side’s talking points into legislation”.

“This is a good bill, and this bill balances marriage equality and religious freedom and it should pass this week without delay,” she said.

The debate on Tuesday was very personal for three MPs who shared stories of their LGBTI children: Liberal MP Andrew Wallace and Labor MPs Cathy O’Toole and Linda Burney.

Wallace said when his daughter came out to him he asked himself “how could this be happening to our family” because “homosexuality went against what I had been taught to believe for many years”.

In time, he accepted that the teachings of church “must not be allowed to override our civil laws”.

O’Toole said one of her daughters planned to hold a commitment ceremony with her partner next year, but that ceremony “can now be a wedding”.

Burney said her son, who was recently found dead after a struggle with mental health and addiction, identified as LGBTI.

“I have seen first-hand the confusion, anxiety and pain that many of our young people experience struggling with their sexuality,” she said.