The Turnbull government's proposed version of marriage equality would further entrench discrimination by allowing civil celebrants and service providers to refuse to undertake gay weddings, the peak law body says.

The Law Council of Australia will on Monday tell a parliamentary inquiry the proposed laws would allow discrimination against same-sex couples on "no proper basis" and undermine fundamental principles of the law.

"The current bill that they're looking at doesn't strike the right balance," council president Fiona McLeod, SC, said. It went "too far" in appeasing religious groups and was "inconsistent with the current federal law", she said.

Despite the same-sex marriage plebiscite being blocked in Parliament, the government has released an exposure draft of its legislation to legalise gay marriage if a plebiscite were to take place and be successful.