Queensland Senator Sue Boyce has spoken out in favour of gay marriage.

Queensland Senator Sue Boyce has spoken out in favour of gay marriage. Photo: Paul Harris

A Liberal senator has broken ranks to speak in favour of gay marriage, as party colleagues began talks on bringing forward a same-sex civil unions bill.

A day after the lower house voted down a Labor private member's bill to allow same-sex marriage, the Senate continued to debate a similar bill.

Queensland senator Sue Boyce told parliament she supported the "intention" of the bill, but accused Labor of cynicism for bringing it on for the debate knowing that it would fail.

"The big news is that gay people are just people," she said.

"There are good gays and bad gays; rich gays and poor gays; gays who want to get married and gays who don't; gays who like footie and gays who don't; gays who want children and those who don't."

It is unclear whether Senator Boyce will cross the floor, but the bill is still likely to fail a vote expected late on Thursday.

Chief opposition whip Warren Entsch said he was talking to colleagues about a civil partnerships bill.

"I have already dusted it out from the drawer. I had it out immediately after the vote," Mr Entsch told ABC radio on Thursday.

"I have already spoken to a number of colleagues."

He acknowledged such a bill was inferior for a part of the community but he believed it had more chance of passing parliament.

"There is also a lot of people out there, and not necessarily in the gay community, who are quite happy to take this up as an alternative," Mr Entsch said.

He said comments from Liberal senator Cory Bernardi during the same-sex marriage debate on Tuesday were "totally inappropriate".

Senator Bernardi resigned from the frontbench team on Wednesday, under pressure from Opposition Leader Tony Abbott, after the South Australian suggested allowing gay marriage could lead to polygamy and bestiality.

Senator Bernardi is heading to a European Young Conservative Freedom Summit in Oxford, England, this weekend.

The UK's Mail Online quoted a Conservative party spokesman as saying: "We strongly condemn Mr Bernardi's comments which don't reflect (Prime Minister) David Cameron's or the Conservative party's viewpoint in any way."

British Labour said his appearance at the event was "astonishing" and accused the Tories of paying "lip service" to equality.

Greens leader Christine Milne noted there were various forms of civil union in a number of states and territories including the ACT, Tasmania, Victoria, NSW and Queensland.

"I would argue that it entrenches discrimination against gay people because it's saying we will entrench the discrimination against gay people because you cannot marry," Senator Milne said.

Labor senator Doug Cameron said the gay community in Australia deserved more than a civil partnerships bill.

AAP