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

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

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".

"We have always made it clear that the protection of religious freedom is an important value," he told 7.30.

"But where you draw the line, how narrowly or how broadly you draw the line, is going to be the subject, no doubt, of a lot of attention during the parliamentary debate."

Sorry, this video has expired George Brandis discusses same-sex marriage and the citizenship debacle

Bill could mean demolishing anti-discrimination laws

The protections contained in Senator Smith's bill would ensure religious ministers and civil celebrants cannot be sued if they refuse to marry same-sex couples.

But Senator Paterson's version has gone much further — allowing private businesses to refuse goods and services for gay weddings if they have "conscientious objections".

Senator Paterson's bill would effectively mean demolishing or overriding existing anti-discrimination laws — which Cabinet Minister Simon Birmingham said the Government had no intention of doing.

"We already have very clear anti-discrimination laws that say you can't turn customers away on the basis of their gender, race, and sexuality and we should not be changing the operation of those laws," Senator Birmingham said.

Senator Paterson's intervention in the debate has infuriated some colleagues, who have questioned whether the Victorian Senator — who voted Yes in the survey — was now trying to burnish his conservative credentials to shore up his pre-selection.

One MP said their "gut turned" when they read the details of Senator Paterson's bill, while another Coalition MP accused him and his conservative colleagues of trying to "torpedo" the process.

There is also an element of frustration among the same-sex marriage supporters, who feel that they have "bent over backwards" to meet the demands of the right-wing of the party — including agreeing to a postal survey.

Depending on the outcome of the survey, Senator Smith is set to table his bill on Thursday, while Senator Paterson is yet to decide whether he will introduce his plan to the Upper House or the party room for further debate.

However, senior members of the Government have made it clear there is little appetite for more debate and the fate of both bills would be decided in Parliament.