Liberal senator Eric Abetz has blamed media bias for not celebrating or honouring people who "come out" and switch from a homosexual to a heterosexual lifestyle.

Labor is expected to finally confirm on Tuesday it will kill off the same-sex marriage plebiscite and vote against it in the Senate, after months of hinting and threatening to do so.

That formal decision, once ticked off by the ALP caucus, leaves the legalisation of same-sex marriage in limbo, with the government unlikely to allow a free vote in the Parliament, despite what some advocates of legal change may claim.

The Turnbull government's proposed amendments to the Marriage Act, which would only be implemented if the plebiscite went ahead and was passed, were due to be examined by a committee on Monday night.