Peers have defeated the government over a "free speech" defence to the law on homophobic hatred.
During consideration of Commons amendments to the Coroners and Justice Bill on 11 November, the Lords voted by 179 to 135, a majority of 44, to uphold the provision despite justice minister Lord Bach calling for the will of the elected chamber to be respected.
Tory former Home Secretary Lord Waddington's "free speech" clause reached the statute book last year after the government ran out of parliamentary time to try to overturn it.
With the parliamentary session due to end on Thursday, ministers will fear the same could happen again as they decide whether to try to overturn it in the 24 hours remaining.
The vote came after the Lords backed down over two other contentious issues in the Coroners and Justice Bill.
In the face of opposition from the Commons, peers accepted intercept evidence should not be used in inquests and that killers who murder their spouse will no longer be able to use the victim's sexual infidelity as a partial defence.
This leaves the disagreement over incitement to hatred on grounds of sexual orientation as the only stumbling block to the bill becoming law this week.
Lord Bach told peers that MPs had voted to overturn the defence on four occasions by majorities of more than 150.
"There must come a point where this House, with all its great virtues, gives way to the House that has been elected by the people of this country," he said.
The last of the votes came on the Coroners and Justice Bill this week when the Government secured a majority of 197 in the Commons to overturn an earlier defeat suffered in the Lords.
The "free speech" defence provides a protection for "discussion or criticism of sexual conduct or practice" to the law on incitement to hatred on the grounds of sexual orientation.
It has been on the statute book since Lord Waddington succeeded in inserting it into last year's Criminal Justice and Immigration Act.