Refusing to serve gay people would be like returning to a time when it was OK to refuse service on religious or racial grounds, according to Labor's Penny Wong.

Key points:

Paterson's bill allows private businesses to refuse goods and services for gay weddings
Wong, Brandis say religious freedoms already well protected in Dean Smith's proposed bill
Smith set to table bill on Thursday, Paterson yet to decide whether to introduce his to Senate or party room

Senator Wong has dismissed Liberal senator James Paterson's proposed bill for same-sex marriage, which includes more protections for same-sex marriage, as a "licence to discriminate".

"I thought we had gone past the point in this country where we had signs that said 'we don't serve Jews, we don't serve blacks'," Senator Wong said.

Senator Wong argued the bill put forward by Liberal senator Dean Smith, which has some exemptions so churches can refuse to conduct same-sex weddings, had appropriate protections.

Senator Smith's plan has attracted broad parliamentary support — but Senator Paterson released an alternative on Monday, which he argued would provide even greater protections for religious freedoms, beyond the ceremony itself.

Some conservatives are deeply concerned the "centre-right" Coalition could be the party to legalise same-sex marriage and see "heavy" religious protections as their only protection against a backlash from party members and supporters.

But Attorney-General George Brandis said the Coalition had "gone to great lengths to make sure this is ultimately the call of the Australian people" and any bill would contain "ample religious protections". Read more via ABC